Orthopedic Board MCQs: Epiphyseal Skeletal Dysplasias

Question 1

A 7-year-old boy presents with bilateral hip pain and a waddling gait. Radiographs reveal bilateral, symmetric fragmentation and flattening of the capital femoral epiphyses, along with irregularity of the acetabula. Radiographs of the spine are entirely normal. Which of the following is the most likely diagnosis?

Explanation

Correct Answer: Multiple Epiphyseal Dysplasia

Multiple Epiphyseal Dysplasia (MED) is characterized by delayed and irregular ossification of the epiphyses. It is distinguished from Legg-Calve-Perthes disease by its bilateral, symmetric nature and the presence of acetabular involvement (Perthes typically has a normal acetabulum initially and is often unilateral or asymmetric). The normal spine differentiates MED from Spondyloepiphyseal Dysplasia (SED), which features platyspondyly.

Question 2

Which of the following genetic mutations is most commonly associated with the autosomal dominant form of Multiple Epiphyseal Dysplasia (MED)?

Explanation

Correct Answer: COMP

The most common mutation in autosomal dominant Multiple Epiphyseal Dysplasia is in the COMP (Cartilage Oligomeric Matrix Protein) gene, located on chromosome 19. Mutations in COL2A1 are associated with Spondyloepiphyseal Dysplasia (SED). FGFR3 mutations cause Achondroplasia, and RUNX2 mutations cause Cleidocranial Dysplasia.

Question 3

A 12-year-old patient with a known skeletal dysplasia presents with knee pain. A lateral radiograph of the knee reveals a 'double-layered' patella. This specific radiographic finding is considered pathognomonic for a mutation in which of the following genes?

Explanation

Correct Answer: SLC26A2

The 'double patella' sign (a double-layered appearance of the patella on a lateral radiograph) is highly characteristic of the autosomal recessive form of Multiple Epiphyseal Dysplasia (rMED), which is caused by mutations in the SLC26A2 gene (a diastrophic dysplasia sulfate transporter). While dominant forms (COMP) can occasionally show patellar abnormalities, the classic double patella is linked to SLC26A2.

Question 4

A 5-year-old boy is evaluated for short stature and a waddling gait. Radiographs demonstrate flattened capital femoral epiphyses, coxa vara, and platyspondyly with anterior wedging of the vertebral bodies. What is the most likely diagnosis?

Explanation

Correct Answer: Spondyloepiphyseal Dysplasia congenita

Spondyloepiphyseal Dysplasia (SED) congenita involves both the epiphyses and the spine. The presence of platyspondyly (flattened vertebral bodies) and anterior wedging is the key differentiator from Multiple Epiphyseal Dysplasia (MED), which typically spares the spine. SED congenita is caused by a defect in type II collagen (COL2A1).

Question 5

A 2-year-old boy undergoes a pelvic radiograph following a minor fall. He is completely asymptomatic. The radiograph incidentally reveals delayed and irregular ossification of bilateral capital femoral epiphyses. There is no involvement of other joints. The condition is expected to resolve spontaneously. What is the diagnosis?

Explanation

Correct Answer: Meyer dysplasia

Meyer dysplasia (dysplasia epiphysealis capitis femoris) is a localized dysplasia of the capital femoral epiphysis characterized by delayed, irregular ossification. It is typically asymptomatic, discovered incidentally in toddlers (usually around age 2), and resolves spontaneously without treatment. It must be differentiated from Perthes disease, which presents later (age 4-8) with pain and necrosis.

Question 6

A 9-year-old patient with Spondyloepiphyseal Dysplasia (SED) congenita is scheduled for elective lower extremity osteotomies. Which of the following preoperative evaluations is absolutely critical to prevent a catastrophic perioperative complication?

Explanation

Correct Answer: Cervical spine flexion-extension radiographs

Patients with Spondyloepiphyseal Dysplasia (SED) congenita frequently have odontoid hypoplasia, which can lead to severe atlantoaxial instability. Flexion-extension radiographs of the cervical spine are mandatory before any surgery requiring general anesthesia and intubation to prevent iatrogenic spinal cord injury during neck manipulation.

Question 7

A newborn presents with short proximal limbs, cataracts, and ichthyosis. Skeletal survey radiographs reveal calcific stippling of the epiphyses around the hips, knees, and ankles. What is the most likely diagnosis?

Explanation

Correct Answer: Chondrodysplasia punctata

Chondrodysplasia punctata is a group of disorders characterized by 'stippled epiphyses' (punctate calcifications in the infantile cartilaginous epiphyses). It is often associated with extra-skeletal manifestations such as cataracts and skin changes (ichthyosis), particularly in the Conradi-Hünermann (X-linked dominant) type.

Question 8

A 28-year-old female with a known history of Multiple Epiphyseal Dysplasia (MED) presents with severe, debilitating bilateral hip pain. Radiographs show end-stage secondary osteoarthritis of both hips with flattened femoral heads, loss of joint space, and incongruent joints. What is the most appropriate definitive management?

Explanation

Correct Answer: Bilateral total hip arthroplasty

Patients with Multiple Epiphyseal Dysplasia (MED) frequently develop premature osteoarthritis in early adulthood due to joint incongruity. Once end-stage osteoarthritis has developed, total joint arthroplasty (THA) is the definitive and most successful treatment. Osteotomies are reserved for younger patients with malalignment before the onset of severe degenerative changes.

Question 9

Pseudoachondroplasia is a skeletal dysplasia that presents with short-limb dwarfism and joint laxity, but normal facial features. It shares its primary genetic mutation with which of the following skeletal dysplasias?

Explanation

Correct Answer: Multiple Epiphyseal Dysplasia

Both Pseudoachondroplasia and the most common autosomal dominant form of Multiple Epiphyseal Dysplasia (MED) are caused by mutations in the COMP (Cartilage Oligomeric Matrix Protein) gene. They are considered part of the same phenotypic spectrum of COMP-opathies, with Pseudoachondroplasia being the more severe clinical manifestation.

Question 10

Which of the following clinical features is typically ABSENT in a patient with classic Multiple Epiphyseal Dysplasia (MED)?

Explanation

Correct Answer: Short-trunk dwarfism

Classic Multiple Epiphyseal Dysplasia (MED) primarily affects the epiphyses of the long bones, leading to mild to moderate short stature (often short-limbed), joint pain, and premature osteoarthritis. The spine is typically spared or only very mildly affected, so short-trunk dwarfism is absent. Short-trunk dwarfism is a hallmark of Spondyloepiphyseal Dysplasia (SED).

Question 11

Which of the following genes is most commonly mutated in the autosomal dominant form of Multiple Epiphyseal Dysplasia (MED), leading to the accumulation of abnormal protein in the rough endoplasmic reticulum of chondrocytes?

Explanation

Correct Answer: B (COMP)

Mutations in the Cartilage Oligomeric Matrix Protein (COMP) gene on chromosome 19 are the most common cause of autosomal dominant Multiple Epiphyseal Dysplasia (MED) and Pseudoachondroplasia. The mutation causes the abnormal COMP protein to accumulate in the rough endoplasmic reticulum of chondrocytes, leading to premature chondrocyte death and disorganized endochondral ossification. COL2A1 is associated with Spondyloepiphyseal Dysplasia Congenita (SEDC). FGFR3 is associated with Achondroplasia. SLC26A2 causes the autosomal recessive form of MED. TRAPPC2 is associated with X-linked Spondyloepiphyseal Dysplasia Tarda.

Question 12

A 10-year-old boy presents with progressive hip pain and a waddling gait. His height is below the 5th percentile, primarily due to a short trunk. Radiographs show flattened vertebral bodies with central humps and dysplastic femoral heads. His father and paternal grandfather have normal stature, but his maternal uncle has early-onset osteoarthritis and short stature. What is the most likely genetic inheritance pattern and associated gene for this condition?

Explanation

Correct Answer: B (X-linked recessive, TRAPPC2)

The clinical picture of short trunk dwarfism presenting in late childhood (tarda) with an X-linked inheritance pattern (maternal uncle affected, father unaffected) points to Spondyloepiphyseal Dysplasia Tarda (SED Tarda). The mutated gene is TRAPPC2 (formerly SEDL), which is inherited in an X-linked recessive manner. SED Congenita (COL2A1) is autosomal dominant and presents at birth. MED (COMP) typically presents with normal or mildly affected trunk height.

Question 13

A 12-year-old girl with mild short stature presents with bilateral knee pain. Lateral radiographs of the knee reveal a 'double-layered' appearance of the patella. Which of the following conditions is most strongly associated with this radiographic finding?

Explanation

Correct Answer: B (Multiple epiphyseal dysplasia)

A double-layered patella (due to delayed or irregular ossification of the patellar epiphysis) is a classic, pathognomonic radiographic sign of Multiple Epiphyseal Dysplasia (MED), particularly the type associated with SLC26A2 (recessive) or COMP mutations. It is best visualized on a lateral radiograph of the knee.

Question 14

A 2-year-old boy is incidentally found to have delayed and irregular ossification of bilateral capital femoral epiphyses on a pelvic radiograph taken for a suspected hernia. He has no limp, normal range of motion, and no pain. What is the most appropriate management?

Explanation

Correct Answer: C (Observation and reassurance)

Meyer dysplasia (dysplasia epiphysealis capitis femoris) is a localized dysplasia of the femoral head characterized by delayed, irregular ossification. It typically presents in children around 2 years of age, is often bilateral, and is asymptomatic. It resolves spontaneously without intervention by age 5-6. It is crucial to differentiate this from Legg-Calvé-Perthes disease, which presents later (4-8 years) with pain, limp, and requires closer monitoring or intervention.

Question 15

A 5-year-old child with Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for bilateral hip reconstruction for severe coxa vara. During the preoperative assessment, which of the following evaluations is most critical to perform before proceeding with general anesthesia?

Explanation

Correct Answer: B (Flexion-extension cervical spine radiographs)

Spondyloepiphyseal Dysplasia Congenita (SEDC) is associated with odontoid hypoplasia, which can lead to severe atlantoaxial instability. Preoperative flexion-extension cervical spine radiographs are critical to assess for instability before intubation and neck positioning to prevent catastrophic spinal cord injury. Aortic root dilation is associated with Marfan syndrome, not SEDC.

Question 16

A newborn is noted to have short proximal limbs, cataracts, and ichthyosis. Radiographs reveal multiple punctate calcifications in the epiphyses of the long bones and the spine. Which of the following maternal exposures during pregnancy can produce a phenocopy of this genetic disorder?

Explanation

Correct Answer: B (Warfarin)

The clinical picture describes Chondrodysplasia Punctata (characterized by stippled epiphyses). Fetal warfarin syndrome (warfarin embryopathy) can produce a phenocopy of this condition, presenting with nasal hypoplasia and stippled epiphyses. Warfarin inhibits vitamin K-dependent proteins (like osteocalcin and matrix Gla protein) which are essential for normal bone and cartilage development.

Question 17

A 4-year-old child presents with disproportionate short stature, a waddling gait, and joint laxity. Radiographs show delayed epiphyseal ossification and irregular, flared metaphyses. The parents note the child's length was normal at birth but growth velocity decreased significantly after age 2. The child has normal facial features and head circumference. What is the most likely diagnosis?

Explanation

Correct Answer: C (Pseudoachondroplasia)

Pseudoachondroplasia is caused by a COMP mutation. Unlike achondroplasia, patients with pseudoachondroplasia have normal birth length, normal craniofacial features (no frontal bossing or midface hypoplasia), and normal intelligence. Growth deceleration becomes apparent around 2-3 years of age. Radiographs show both epiphyseal and metaphyseal involvement, distinguishing it from pure epiphyseal dysplasias.

Question 18

A 7-year-old boy with a known COL2A1 mutation presents with a short trunk, barrel chest, and severe coxa vara. Given his underlying diagnosis of Spondyloepiphyseal Dysplasia Congenita, he should be routinely screened by an ophthalmologist to prevent which of the following complications?

Explanation

Correct Answer: C (Retinal detachment)

Spondyloepiphyseal Dysplasia Congenita (SEDC) is a type II collagenopathy caused by mutations in the COL2A1 gene. Type II collagen is a major structural component of the vitreous humor of the eye. Patients are highly susceptible to high myopia and retinal detachment, necessitating regular ophthalmologic screening to prevent blindness.

Question 19

A 9-year-old child presents with joint pain and mild short stature. The orthopedic surgeon is trying to differentiate between Multiple Epiphyseal Dysplasia (MED) and Spondyloepiphyseal Dysplasia (SED). Which of the following radiographic findings of the spine would most strongly support a diagnosis of MED over SED?

Explanation

Correct Answer: C (Normal vertebral body height with mild endplate irregularities)

The key differentiating factor between MED and SED is the degree of spinal involvement. In MED, the spine is typically normal or shows only mild irregularities (e.g., Schmorl's nodes, mild endplate changes), and stature is only mildly affected. In SED, there is significant spinal involvement, typically presenting as platyspondyly (flattened vertebrae) leading to short trunk dwarfism.

Question 20

A 14-year-old male with Multiple Epiphyseal Dysplasia presents with bilateral hip pain. Radiographs show flattened, irregular capital femoral epiphyses with early signs of secondary osteoarthritis, but the acetabula are relatively well-preserved. If surgical intervention is considered to prolong the lifespan of the native hip, which of the following is the most appropriate rationale for an intertrochanteric osteotomy in this patient?

Explanation

Correct Answer: B (To redirect a more congruent portion of the femoral head into the weight-bearing zone)

In MED, the femoral heads become flattened and irregular, leading to early osteoarthritis. If a portion of the femoral head is more congruent with the acetabulum (often assessed via dynamic radiographs or MRI), a proximal femoral osteotomy (varus or valgus, flexion or extension) can be performed to redirect this congruent cartilage into the primary weight-bearing zone. This improves joint mechanics and can delay the need for total hip arthroplasty.

Question 21

A 6-year-old boy presents with waddling gait, joint pain, and short stature. Radiographs reveal delayed, irregular ossification of multiple epiphyses. Genetic testing confirms a mutation in the COMP (Cartilage Oligomeric Matrix Protein) gene. Which of the following radiographic findings is most classically associated with this patient's condition?

Explanation

Correct Answer: Double-layer patella on lateral knee radiograph

This patient has Multiple Epiphyseal Dysplasia (MED), most commonly caused by mutations in the COMP gene (Fairbank type). A classic, though not entirely pathognomonic, radiographic finding in MED is the 'double-layer' patella seen on a lateral knee radiograph. Severe platyspondyly is characteristic of Spondyloepiphyseal Dysplasia (SED), not MED. Stippled epiphyses are seen in Chondrodysplasia Punctata. Erlenmeyer flask deformity is seen in osteopetrosis and Gaucher disease. Rugger jersey spine is associated with renal osteodystrophy.

Question 22

A 4-year-old child is evaluated for an asymmetric, painless swelling over the medial aspect of the right ankle. Radiographs show an irregular, ossified mass arising from the medial epiphysis of the distal tibia. A biopsy is performed. What is the expected histological appearance of this lesion?

Explanation

Correct Answer: Histologically identical to an osteochondroma

The clinical and radiographic presentation is classic for Dysplasia Epiphysealis Hemimelica (Trevor disease). This is a rare developmental disorder characterized by an asymmetric cartilaginous overgrowth of an epiphysis, most commonly affecting the lower extremity (medial side of the distal femur, distal tibia, or talus). Histologically, the lesion is indistinguishable from an osteochondroma, featuring a cartilage cap overlying trabecular bone that is continuous with the underlying epiphysis.

Question 23

A 5-year-old child with Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for bilateral proximal femoral osteotomies to treat severe coxa vara. Which of the following preoperative evaluations is absolutely mandatory before proceeding with surgery?

Explanation

Correct Answer: Cervical spine flexion-extension radiographs

Spondyloepiphyseal Dysplasia Congenita (SEDC) is a type II collagenopathy (COL2A1 mutation). It is strongly associated with odontoid hypoplasia and os odontoideum, leading to atlantoaxial instability. Preoperative cervical spine clearance with flexion-extension radiographs is mandatory before any procedure requiring anesthesia and intubation to prevent catastrophic spinal cord injury. Aortic root dilation is associated with Marfan syndrome, not SEDC.

Question 24

A 3-year-old boy is incidentally found to have delayed and irregular ossification of bilateral capital femoral epiphyses on a pelvic radiograph taken for a suspected urinary tract infection. He has no limp and no hip pain. Which of the following statements best differentiates this condition from Legg-Calvé-Perthes disease?

Explanation

Correct Answer: This condition shows a fragmented appearance that resolves spontaneously without epiphyseal collapse.

The clinical scenario describes Meyer dysplasia, a benign, often asymptomatic condition characterized by delayed and irregular ossification of the capital femoral epiphysis. It typically presents in children aged 2 to 3 years and is frequently bilateral. Unlike Legg-Calvé-Perthes disease, Meyer dysplasia does not progress to epiphyseal collapse or severe deformity, and it resolves spontaneously without the need for surgical containment or bracing.

Question 25

A neonate presents with severe shortening of the proximal limbs, cataracts, and ichthyosis. Radiographs reveal multiple punctate calcifications in the epiphyses of the long bones and spine. Which of the following maternal exposures during pregnancy can produce a phenocopy of this genetic skeletal dysplasia?

Explanation

Correct Answer: Warfarin

The neonate's presentation is consistent with Chondrodysplasia Punctata (stippled epiphyses). Fetal warfarin syndrome (warfarin embryopathy) can cause a phenocopy of this condition, presenting with nasal hypoplasia, stippled epiphyses, and limb hypoplasia. Warfarin inhibits vitamin K-dependent proteins, including osteocalcin and matrix Gla protein, which are essential for normal bone and cartilage development.

Question 26

A 12-year-old boy presents with progressive back pain and bilateral hip pain. Radiographs show mild platyspondyly with a characteristic 'hump-shaped' build-up of bone on the central and posterior portions of the vertebral endplates. His maternal uncle has a similar history of early-onset osteoarthritis. What is the inheritance pattern of this specific skeletal dysplasia?

Explanation

Correct Answer: X-linked recessive

The clinical and radiographic presentation (hump-shaped vertebral endplates, male patient, maternal uncle affected) is classic for Spondyloepiphyseal Dysplasia (SED) Tarda. SED Tarda is caused by mutations in the TRAPPC2 gene and is inherited in an X-linked recessive pattern. It typically presents in late childhood or adolescence with back pain and premature osteoarthritis of the hips and shoulders.

Question 27

When differentiating Multiple Epiphyseal Dysplasia (MED) from Spondyloepiphyseal Dysplasia (SED) radiographically, which of the following findings is the most reliable distinguishing feature?

Explanation

Correct Answer: MED typically lacks significant spinal involvement, whereas SED features marked platyspondyly.

The primary distinguishing feature between MED and SED is the extent of spinal involvement. MED primarily affects the epiphyses of the appendicular skeleton, and spinal involvement is usually absent or very mild (e.g., mild endplate irregularities). In contrast, SED (Spondyloepiphyseal Dysplasia) inherently involves the spine, classically presenting with marked platyspondyly (flattened vertebrae) and other axial deformities.

Question 28

A 7-year-old girl with Dysplasia Epiphysealis Hemimelica (Trevor disease) of the distal medial femur is undergoing evaluation for surgical excision due to progressive angular deformity and joint mechanical symptoms. Which of the following is the most significant complication associated with the surgical excision of these lesions?

Explanation

Correct Answer: Premature physeal closure leading to growth arrest and worsening angular deformity

Surgical excision of the epiphyseal overgrowth in Trevor disease is technically challenging because the mass arises directly from the epiphysis and is intimately associated with the physis and articular cartilage. The most significant complication of excision is iatrogenic damage to the physis, which can lead to premature physeal closure, subsequent growth arrest, and worsening of the angular deformity.

Question 29

A 4-year-old child with Spondyloepiphyseal Dysplasia Congenita (SEDC) is being evaluated in a multidisciplinary clinic. Because SEDC is a type II collagenopathy, which of the following extraskeletal manifestations requires rigorous routine screening in this patient?

Explanation

Correct Answer: Retinal detachment

Spondyloepiphyseal Dysplasia Congenita (SEDC) is caused by mutations in the COL2A1 gene, which encodes type II collagen. Type II collagen is a major structural component of articular cartilage, the nucleus pulposus, and the vitreous humor of the eye. Consequently, patients with SEDC are at a very high risk for severe myopia and retinal detachment. Routine, rigorous ophthalmologic screening is essential to prevent blindness.

Question 30

Which of the following genetic mutations is responsible for the autosomal recessive form of Chondrodysplasia Punctata (Rhizomelic type), which is characterized by severe proximal limb shortening, profound intellectual disability, and early lethality?

Explanation

Correct Answer: PEX7 gene mutation affecting peroxisomal biogenesis

Rhizomelic Chondrodysplasia Punctata (RCDP) is an autosomal recessive disorder characterized by severe rhizomelic shortening, stippled epiphyses, cataracts, and severe intellectual disability. It is a peroxisomal biogenesis disorder, most commonly caused by mutations in the PEX7 gene, which leads to a defect in the plasmalogen biosynthesis pathway. FGFR3 is associated with achondroplasia. COL1A1 is associated with osteogenesis imperfecta. COMP is associated with MED and pseudoachondroplasia. SOX9 is associated with campomelic dysplasia.

Question 31

Multiple epiphyseal dysplasia (MED) is most commonly associated with an autosomal dominant mutation in the COMP gene. What is the primary function of the protein encoded by this gene in the articular cartilage matrix?

Explanation

Correct Answer: C

The COMP (Cartilage Oligomeric Matrix Protein) gene encodes a pentameric non-collagenous glycoprotein that plays a crucial role in catalyzing collagen fibril assembly and stabilizing the extracellular matrix of cartilage. Mutations in COMP lead to the accumulation of misfolded proteins in the rough endoplasmic reticulum of chondrocytes, causing premature chondrocyte death and resulting in Multiple Epiphyseal Dysplasia (MED) or Pseudoachondroplasia. Type II collagen (Option A) provides tensile strength. Sulfate transport (Option B) is related to the SLC26A2 gene (diastrophic dysplasia/recessive MED).

Question 32

A 10-year-old boy presents with progressive hip pain and a waddling gait. Physical examination reveals a short trunk but normal limb length. Radiographs reveal platyspondyly with a characteristic 'hump-shaped' buildup of bone on the central and posterior portions of the vertebral endplates. His maternal uncle has a similar condition. What is the most likely genetic inheritance pattern of this disorder?

Explanation

Correct Answer: D

The clinical presentation of short-trunk dwarfism presenting in late childhood, combined with the pathognomonic radiographic finding of 'hump-shaped' vertebral endplates, is classic for Spondyloepiphyseal Dysplasia (SED) Tarda. SED Tarda is inherited in an X-linked recessive pattern and is caused by mutations in the TRAPPC2 (formerly SEDL) gene. It primarily affects males, which aligns with the history of the maternal uncle being affected. SED Congenita, in contrast, is autosomal dominant (COL2A1 mutation) and presents at birth.

Question 33

A 6-year-old child is evaluated for bilateral hip pain and a waddling gait. Radiographs show delayed, fragmented ossification of both capital femoral epiphyses. Which of the following radiographic findings would most strongly support a diagnosis of Multiple Epiphyseal Dysplasia (MED) rather than bilateral Legg-Calvé-Perthes disease?

Explanation

Correct Answer: C

Differentiating MED from bilateral Legg-Calvé-Perthes disease can be challenging as both present with fragmented, irregular capital femoral epiphyses. However, MED is a systemic dysplasia affecting multiple epiphyses. A classic radiographic hallmark of MED is the 'double patella' (a double-layered appearance of the patella on a lateral knee radiograph), which is seen in a significant percentage of patients. Severe platyspondyly (Option D) would suggest Spondyloepiphyseal Dysplasia (SED), as the spine is typically normal or only mildly affected in MED. Crescent signs and coxa magna are common in Perthes disease.

Question 34

A 4-year-old child with Spondyloepiphyseal Dysplasia (SED) congenita is scheduled for bilateral hip reconstruction due to severe coxa vara. During the preoperative evaluation, which of the following is the most critical screening study required before proceeding with general anesthesia?

Explanation

Correct Answer: B

Patients with Spondyloepiphyseal Dysplasia (SED) congenita (caused by COL2A1 mutations) frequently have odontoid hypoplasia, which can lead to severe atlantoaxial instability. Before any surgical procedure requiring general anesthesia and intubation, it is critical to obtain flexion-extension radiographs of the cervical spine to evaluate for C1-C2 instability to prevent catastrophic spinal cord injury during neck manipulation. Aortic root dilation (Option A) is a concern in Marfan syndrome, not typically SED.

Question 35

A 2-year-old boy is incidentally found to have delayed and irregular ossification of the bilateral capital femoral epiphyses on a pelvic radiograph taken for a suspected swallowed coin. He has no limp, normal range of motion, and no pain. What is the most appropriate management for this orthopedic finding?

Explanation

Correct Answer: D

The clinical scenario describes Meyer dysplasia (dysplasia epiphysealis capitis femoris), which is characterized by delayed and irregular ossification of the capital femoral epiphyses. It typically presents incidentally in toddlers (usually around 2 years of age) and is bilateral in about 50% of cases. Unlike Legg-Calvé-Perthes disease, Meyer dysplasia is a benign, self-limiting condition that does not progress to avascular necrosis or collapse. Therefore, the most appropriate management is observation and reassurance. No surgical or orthotic intervention is required.

Question 36

A newborn is noted to have short proximal limbs, cataracts, and ichthyosis. Radiographs reveal multiple punctate calcifications in the epiphyses of the long bones and the cartilaginous portions of the spine. Which of the following maternal exposures during pregnancy can produce a phenocopy of this genetic skeletal dysplasia?

Explanation

Correct Answer: B

The clinical and radiographic description is classic for Chondrodysplasia Punctata (stippled epiphyses). Maternal use of Warfarin during pregnancy (fetal warfarin syndrome or warfarin embryopathy) can cause a phenocopy of this genetic disorder. Warfarin inhibits vitamin K-dependent proteins, including osteocalcin and matrix Gla protein, leading to abnormal bone and cartilage calcification, resulting in stippled epiphyses, nasal hypoplasia, and short limbs. Thalidomide (Option E) causes phocomelia, not stippled epiphyses.

Question 37

Both Multiple Epiphyseal Dysplasia (Fairbank type) and Pseudoachondroplasia can be caused by mutations in the Cartilage Oligomeric Matrix Protein (COMP) gene. Which of the following clinical or radiographic features best distinguishes Pseudoachondroplasia from Multiple Epiphyseal Dysplasia?

Explanation

Correct Answer: B

While both MED and Pseudoachondroplasia can result from COMP gene mutations, Pseudoachondroplasia is generally more severe. The key distinguishing feature is that Pseudoachondroplasia involves significant metaphyseal irregularities, flaring, and shortening, in addition to epiphyseal dysplasia. MED is predominantly confined to the epiphyses with minimal to no metaphyseal involvement. Both conditions typically have a normal facial appearance (Option A), distinguishing them from true achondroplasia. Both are autosomal dominant (Option C) and lead to early osteoarthritis (Option D).

Question 38

A 7-year-old girl with Spondyloepiphyseal Dysplasia (SED) congenita presents for a routine orthopedic follow-up. In addition to monitoring her spine and hips, the orthopedic surgeon must ensure she is receiving regular evaluations by which of the following specialists due to a high-risk associated condition?

Explanation

Correct Answer: B

SED congenita is a type II collagenopathy caused by mutations in the COL2A1 gene. Type II collagen is a major structural component of articular cartilage, the nucleus pulposus, and the vitreous humor of the eye. Consequently, patients with SED congenita are at a very high risk for severe myopia and retinal detachment. Regular ophthalmologic screening is mandatory to prevent blindness. The other options are not classically associated with SED congenita.

Question 39

While most forms of Multiple Epiphyseal Dysplasia (MED) are autosomal dominant, an autosomal recessive form exists due to mutations in the SLC26A2 gene (diastrophic dysplasia sulfate transporter). Which of the following clinical features is characteristic of this specific recessive variant and helps distinguish it from dominant MED?

Explanation

Correct Answer: B

Mutations in the SLC26A2 gene cause a spectrum of recessive skeletal dysplasias, ranging from lethal achondrogenesis type IB to diastrophic dysplasia and recessive MED (rMED). Recessive MED is distinguished from dominant MED by the presence of features overlapping with diastrophic dysplasia, such as clubfoot (talipes equinovarus), cleft palate, and cystic swelling of the ear pinnae (cauliflower ear). Retinal detachment (Option A) is seen in COL2A1 mutations (SED). Cervical kyphosis (Option C) is classic for diastrophic dysplasia but less prominent in rMED, though clubfoot and ear findings are key differentiators for the SLC26A2 spectrum.

Question 40

A 14-year-old boy is diagnosed with X-linked Spondyloepiphyseal Dysplasia Tarda. Which of the following is the pathognomonic radiographic finding in the spine for this condition?

Explanation

Correct Answer: C

The pathognomonic radiographic finding for X-linked Spondyloepiphyseal Dysplasia Tarda is a central, hump-shaped buildup of bone on the superior and inferior endplates of the vertebral bodies, predominantly in the posterior two-thirds. This is due to a failure of ossification of the ring apophysis. Anterior beaking (Option A) is seen in mucopolysaccharidoses (like Morquio or Hurler syndrome). 'Picture-frame' vertebrae (Option B) are seen in Paget's disease. 'Rugger-jersey' spine (Option D) is seen in renal osteodystrophy. Coronal clefts (Option E) are seen in chondrodysplasia punctata.

Question 41

A 9-year-old boy presents with bilateral knee pain and a waddling gait. Radiographs reveal delayed, fragmented ossification centers of the proximal femurs and a characteristic 'double-layered' appearance of the patella on the lateral knee radiograph. He also has a history of bilateral clubfeet treated in infancy. Which of the following gene mutations is most likely responsible for this specific phenotype?

Explanation

Correct Answer: B (SLC26A2)

This patient presents with the classic features of autosomal recessive Multiple Epiphyseal Dysplasia (rMED). While most cases of MED are autosomal dominant (commonly involving the COMP gene), the recessive form is caused by mutations in the SLC26A2 gene (which encodes a sulfate transporter). A pathognomonic radiographic finding for rMED is the 'double-layered' patella. Patients also frequently present with clubfeet (talipes equinovarus) and cystic ear swellings (cauliflower ear). COL2A1 is associated with Spondyloepiphyseal Dysplasia (SED), and FGFR3 is associated with Achondroplasia.

Question 42

A 5-year-old boy presents with a painless, asymmetric, hard swelling on the medial aspect of his right ankle. Radiographs demonstrate an irregular, stippled ossification mass arising directly from the medial epiphysis of the distal tibia. If this lesion were to be excised and examined histologically, the tissue would most closely resemble which of the following?

Explanation

Correct Answer: A (Osteochondroma)

The clinical and radiographic presentation is classic for Dysplasia Epiphysealis Hemimelica (also known as Trevor disease). This is a rare developmental disorder characterized by asymmetric cartilage overgrowth in the epiphyses, most commonly affecting the medial side of the lower extremity (ankle or knee). Histologically, the lesion is indistinguishable from an osteochondroma, consisting of a cartilage cap with underlying endochondral ossification. It is essentially an intra-articular osteochondroma arising from the epiphysis.

Question 43

A 12-year-old boy presents with short stature, primarily affecting his trunk, and progressive hip pain. Radiographs reveal platyspondyly with a characteristic 'hump-shaped' central buildup of bone on the vertebral endplates, and dysplastic capital femoral epiphyses. His father is of normal height, but his maternal uncle has a similar condition. What is the most likely genetic inheritance pattern and associated gene?

Explanation

Correct Answer: B (X-linked recessive, TRAPPC2)

The patient has Spondyloepiphyseal Dysplasia (SED) Tarda. The key distinguishing features are the later onset (usually late childhood), X-linked recessive inheritance (affecting males, with maternal uncles affected), and the pathognomonic 'hump-shaped' central buildup of bone on the superior and inferior vertebral endplates seen on lateral spine radiographs. It is caused by mutations in the TRAPPC2 (formerly SEDL) gene. SED Congenita, in contrast, is autosomal dominant, caused by COL2A1 mutations, and presents at birth.

Question 44

A 2-year-old boy is incidentally found to have delayed and granular ossification of the bilateral capital femoral epiphyses on a pelvic radiograph taken for a suspected urinary tract infection. He has no limp, no hip pain, and a completely normal range of motion. What is the most appropriate management for this orthopedic finding?

Explanation

Correct Answer: D (Observation and reassurance)

This presentation is highly characteristic of Meyer dysplasia (dysplasia epiphysealis capitis femoris). It is a benign, self-limiting condition characterized by delayed and irregular ossification of the capital femoral epiphysis. It is typically bilateral, asymptomatic, and discovered incidentally in toddlers. It is crucial to differentiate it from Legg-Calvé-Perthes disease, which usually presents later (ages 4-8) with pain and a limp. Meyer dysplasia requires no treatment and typically resolves with normal ossification by age 6.

Question 45

A newborn female presents with asymmetric limb shortening, ichthyosiform skin lesions, and bilateral cataracts. Radiographs demonstrate widespread stippled calcifications in the epiphyses of the long bones and the spine. Which of the following is the most likely diagnosis?

Explanation

Correct Answer: B (Conradi-Hünermann syndrome)

The presence of stippled epiphyses (chondrodysplasia punctata) narrows the differential. Conradi-Hünermann syndrome is the X-linked dominant form of chondrodysplasia punctata. It is typically lethal in males, so it is seen almost exclusively in females. Classic features include asymmetric limb shortening, ichthyosis, cataracts, and stippled epiphyses. Rhizomelic chondrodysplasia punctata is autosomal recessive, presents with symmetric proximal limb shortening, and is usually lethal in the first year of life.

Question 46

A 28-year-old female with a known diagnosis of Multiple Epiphyseal Dysplasia (MED) presents with severe, bilateral hip pain that limits her daily activities. Radiographs show advanced bilateral hip osteoarthritis with flattened femoral heads, but her acetabular depth is relatively preserved. Spine radiographs are normal. Which of the following is the most appropriate surgical intervention?

Explanation

Correct Answer: C (Bilateral total hip arthroplasty)

Patients with Multiple Epiphyseal Dysplasia (MED) frequently develop early-onset, severe osteoarthritis of the weight-bearing joints, particularly the hips and knees, due to the incongruity of the dysplastic epiphyses. In a young adult with end-stage osteoarthritis severely limiting function, Total Hip Arthroplasty (THA) is the treatment of choice and provides excellent pain relief and functional improvement. Joint-preserving osteotomies are generally not effective once advanced degenerative changes have occurred.

Question 47

A 6-year-old child with Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for bilateral proximal femoral osteotomies to correct severe coxa vara. During the preoperative evaluation, which of the following is the most critical screening test to perform before proceeding with general anesthesia?

Explanation

Correct Answer: B (Flexion-extension radiographs of the cervical spine)

Spondyloepiphyseal Dysplasia Congenita (SEDC), caused by COL2A1 mutations, is strongly associated with odontoid hypoplasia and subsequent atlantoaxial instability. This is a critical, potentially life-threatening issue during intubation and positioning for surgery under general anesthesia. Therefore, obtaining flexion-extension radiographs of the cervical spine is a mandatory preoperative screening step to assess for instability. If instability is present, careful intubation techniques (e.g., fiberoptic) and potentially cervical fusion are required.

Question 48

A 10-year-old patient presents with short stature and joint pain. Radiographs reveal flattened, irregular epiphyses in the knees, hips, and ankles. To reliably differentiate Multiple Epiphyseal Dysplasia (MED) from Spondyloepiphyseal Dysplasia (SED), which of the following radiographic assessments is most definitive?

Explanation

Correct Answer: A (Lateral radiograph of the thoracolumbar spine)

The primary distinguishing feature between Multiple Epiphyseal Dysplasia (MED) and Spondyloepiphyseal Dysplasia (SED) is the involvement of the spine. In MED, the spine is typically normal or shows only mild, clinically insignificant changes (like mild endplate irregularities). In SED, there is significant spinal involvement, most notably platyspondyly (flattened vertebral bodies), which contributes to a disproportionate short-trunk short stature. Therefore, a lateral spine radiograph is the most definitive test to differentiate the two.

Question 49

A 7-year-old boy undergoes surgical excision of a symptomatic Dysplasia Epiphysealis Hemimelica (Trevor disease) lesion located on the medial aspect of the distal femoral epiphysis. Which of the following is the most likely long-term complication of this surgical intervention?

Explanation

Correct Answer: B (Premature physeal closure and angular deformity)

Trevor disease (Dysplasia Epiphysealis Hemimelica) involves an osteochondroma-like overgrowth arising directly from the epiphysis. Surgical excision is often indicated for pain, mechanical block to motion, or progressive deformity. However, because the lesion is intimately associated with the epiphysis and the adjacent physis, surgical excision carries a high risk of iatrogenic injury to the growth plate. This frequently leads to premature physeal closure, resulting in growth arrest and subsequent angular deformity.

Question 50

Which of the following radiographic findings in the hands is most characteristic of Multiple Epiphyseal Dysplasia (MED)?

Explanation

Correct Answer: C (Delayed ossification of the carpal bones with short, stubby metacarpals and phalanges)

Multiple Epiphyseal Dysplasia (MED) affects the epiphyses of long bones and the small bones of the hands and feet. Characteristic hand radiograph findings include delayed ossification of the carpal bones and brachydactyly (short, stubby metacarpals and phalanges). A 'trident hand' is classic for Achondroplasia. Madelung deformity is seen in Leri-Weill dyschondrosteosis. Proximal pointing of the metacarpals is a hallmark of Mucopolysaccharidoses (e.g., Hurler syndrome). Arachnodactyly is characteristic of Marfan syndrome.

Question 51

A 4-year-old boy presents with an asymmetric, painless swelling on the medial side of his right ankle. Radiographs show irregular, lobulated, cartilaginous overgrowth arising from the medial epiphysis of the distal tibia. A biopsy is performed. Which of the following best describes the expected histologic findings?

Explanation

Dysplasia epiphysealis hemimelica (Trevor disease) represents an intra-articular osteochondroma-like lesion arising from an epiphysis. Histologically, it is indistinguishable from a classic osteochondroma.

Question 52

Pseudoachondroplasia and certain forms of Multiple Epiphyseal Dysplasia (MED) are caused by mutations in the Cartilage Oligomeric Matrix Protein (COMP) gene. Which of the following best describes the cellular pathogenesis of these conditions?

Explanation

Mutations in the COMP gene lead to the synthesis of a misfolded protein that accumulates within the rough endoplasmic reticulum of chondrocytes. This accumulation causes severe ER stress, leading to premature chondrocyte apoptosis and impaired endochondral ossification.

Question 53

A 6-year-old child with a known diagnosis of Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for elective bilateral femoral osteotomies to correct severe coxa vara. During preoperative planning, which of the following evaluations is absolutely critical before proceeding with general anesthesia?

Explanation

Patients with SEDC frequently have odontoid hypoplasia, leading to atlantoaxial instability. Flexion-extension cervical spine radiographs are critical prior to general anesthesia to avoid catastrophic neurologic injury during intubation.

Question 54

A 12-year-old boy presents with short stature, broad chest, and progressively worsening hip and back pain. Radiographs of his spine demonstrate generalized platyspondyly with a characteristic 'heaped-up' accumulation of bone at the posterior aspect of the vertebral endplates. Which of the following inheritance patterns is most likely associated with this patient's condition?

Explanation

The clinical and radiographic presentation is classic for Spondyloepiphyseal Dysplasia (SED) Tarda, characterized by late-childhood onset and 'hump-shaped' posterior vertebral bodies. It is an X-linked recessive disorder caused by mutations in the TRAPPC2 gene.

Question 55

A 4-year-old boy presents with disproportionate short-trunk short stature, a flat midface, and coxa vara. His hands and feet are of normal size. Radiographs reveal delayed epiphyseal ossification and marked platyspondyly. Which of the following genes is most likely mutated in this patient?

Explanation

Spondyloepiphyseal Dysplasia Congenita (SEDC) is caused by autosomal dominant mutations in the COL2A1 gene. It is characterized by short-trunk dwarfism, coxa vara, and platyspondyly, while the hands and feet typically remain normal.

Question 56

A 3-year-old child presents with severe joint hyperlaxity, a waddling gait, and disproportionate short stature. Radiographs show delayed epiphyseal ossification and irregular, fragmented metaphyses. Which craniofacial feature distinguishes this patient's most likely diagnosis from achondroplasia?

Explanation

This presentation is highly characteristic of pseudoachondroplasia (COMP gene mutation). Unlike achondroplasia, patients with pseudoachondroplasia have completely normal craniofacial features and head circumferences.

Question 57

A 5-year-old boy presents with a painless, hard swelling on the medial aspect of his left ankle that is restricting his range of motion. Radiographs show an asymmetric, irregular ossified mass arising directly from the distal tibial epiphysis. Histology of a biopsy would most likely show which of the following?

Explanation

Dysplasia epiphysealis hemimelica (Trevor's disease) is characterized by asymmetric epiphyseal cartilage overgrowth. Histologically, the lesions are indistinguishable from osteochondromas, featuring a benign hyaline cartilage cap.

Question 58

A 12-year-old boy is evaluated for recent-onset back pain and short stature. Radiographs demonstrate narrowed intervertebral disc spaces and a barrel-shaped chest. Spondyloepiphyseal Dysplasia Tarda (SEDT) is suspected. What is the mode of inheritance for the most common form of this disease?

Explanation

The most common form of SEDT is X-linked recessive, primarily affecting males in late childhood. It is caused by mutations in the TRAPPC2 gene.

Question 59

An infant is born with asymmetric limb shortening, cataracts, and ichthyosis. Skeletal survey reveals punctate calcifications of the epiphyses. The mother had no complications or medication usage during pregnancy. Which of the following is the most likely mode of inheritance for this patient's condition?

Explanation

Conradi-Hünermann syndrome is the X-linked dominant form of chondrodysplasia punctata, caused by mutations in the EBP gene. It predominantly affects females and is classically associated with asymmetric limb shortening and ichthyosis.

Question 60

A 6-year-old patient with an established diagnosis of Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for elective knee realignment surgery. Which of the following preoperative evaluations is most critical for this patient?

Explanation

Patients with SEDC are at high risk for odontoid hypoplasia and subsequent atlantoaxial instability. Flexion-extension cervical spine radiographs are mandatory before any procedure requiring general anesthesia to prevent catastrophic spinal cord injury during intubation.

Question 61

Which of the following describes the primary cellular pathogenesis of the COMP gene mutation responsible for pseudoachondroplasia?

Explanation

Mutations in the COMP gene cause misfolded Cartilage Oligomeric Matrix Protein to aggregate in the rough endoplasmic reticulum. This leads to progressive cellular toxicity, premature chondrocyte death, and impaired enchondral ossification.

Question 62

A 14-year-old male with a TRAPPC2 mutation undergoes routine radiographic evaluation of the spine. Which of the following findings is considered pathognomonic for his diagnosis?

Explanation

Spondyloepiphyseal Dysplasia Tarda (SEDT) exhibits a pathognomonic radiographic appearance of the spine. A mound or "hump" of heaped-up bone forms on the central and posterior portions of the vertebral endplates.

Question 63

A 3-year-old child presents with severe joint stiffness and prominent, enlarged joints. A skeletal survey reveals dumbbell-shaped femora and distinct coronal clefts in the vertebral bodies. Which of the following is the most likely diagnosis?

Explanation

Kniest dysplasia is a severe type II collagenopathy (COL2A1 mutation). It is classically identified by clinical joint enlargement and radiographic findings of dumbbell-shaped long bones and coronal vertebral clefts.

Question 64

A 9-year-old boy with Spondyloepiphyseal Dysplasia Congenita presents for his annual orthopedic follow-up. In addition to monitoring his cervical spine and hip development, routine screening by which of the following specialists is most important due to his genetic defect?

Explanation

SEDC is caused by a COL2A1 mutation affecting type II collagen, which is abundant in the vitreous humor of the eye. These patients are at a high risk for extreme myopia and early retinal detachment.

Question 65

A 7-year-old boy with Dysplasia epiphysealis hemimelica (Trevor disease) of the distal femur presents with a worsening mechanical block to knee flexion and increasing pain. What is the most appropriate management?

Explanation

Symptomatic Trevor disease causing a mechanical block or deformity is managed with surgical excision. It is critical to meticulously remove the epiphyseal mass while preserving the normal underlying chondral surface and joint congruity.

Question 66

A 32-year-old patient with Autosomal Dominant Multiple Epiphyseal Dysplasia (MED) presents with end-stage hip osteoarthritis and requires bilateral total hip arthroplasties (THA). Which of the following intraoperative challenges is most characteristic for this specific patient population?

Explanation

Patients with MED frequently develop early-onset OA due to dysplastic epiphyses. THA is technically demanding because these patients characteristically have narrow diaphyseal canals and dwarfed, deformed proximal femora, frequently requiring custom implants.

Question 67

An infant is evaluated for profound developmental delay, cataracts, and severe rhizomelic shortening of the limbs. Radiographs show punctate epiphyseal calcifications. Genetic testing reveals a mutation in the PEX7 gene. Which of the following metabolic processes is fundamentally impaired?

Explanation

Rhizomelic chondrodysplasia punctata is an autosomal recessive disorder caused by mutations in PEX7. This leads to defective peroxisome biogenesis, causing severe neurodevelopmental deficits and early mortality.

Question 68

An 8-year-old patient with an established diagnosis of Spondyloepiphyseal Dysplasia Congenita (SEDC) presents with a new onset of gait clumsiness, bilateral lower extremity weakness, and hyperreflexia. What is the most appropriate next step in management?

Explanation

Clumsiness, weakness, and hyperreflexia in an SEDC patient strongly suggest cervical myelopathy due to atlantoaxial instability from odontoid hypoplasia. An urgent MRI of the cervical spine is required to evaluate for spinal cord compression.

Question 69

A 4-year-old child with disproportionate short trunk dwarfism and a barrel chest is scheduled for elective hernia repair. Radiographs show delayed ossification of the pubic bones and epiphyses, as well as platyspondyly. Which of the following preoperative evaluations is most critical for this patient?

Explanation

This patient has Spondyloepiphyseal Dysplasia Congenita (SEDC), caused by a COL2A1 mutation. Due to the high risk of odontoid hypoplasia and atlantoaxial instability, cervical spine radiographs are mandatory before any procedure requiring intubation.

Question 70

A 6-year-old boy presents with an asymmetric, painless swelling on the medial aspect of his right ankle. Radiographs show an irregular, ossified mass arising from the medial epiphysis of the distal tibia. Histological examination of the lesion is most likely to resemble which of the following benign tumors?

Explanation

Dysplasia epiphysealis hemimelica (Trevor disease) is an asymmetric overgrowth of articular cartilage, typically in the lower extremities. Histologically, it is indistinguishable from an osteochondroma, possessing a cartilage cap and underlying trabecular bone.

Question 71

A 12-year-old boy presents with back pain and decreasing height percentile. Radiographs reveal flattened vertebral bodies with a pathognomonic 'heaped-up' appearance on the posterior portion of the superior endplates. Which of the following is the correct inheritance pattern and mutated gene for this condition?

Explanation

The patient has Spondyloepiphyseal Dysplasia Tarda, characterized by a hump-shaped mound of bone on the posterior superior vertebral endplates. It is inherited in an X-linked recessive pattern due to mutations in the TRAPPC2 (SEDL) gene.

Question 72

A 3-year-old girl is evaluated for a waddling gait and short stature. Clinical examination reveals completely normal facial features and head circumference, but marked shortening of the limbs. Radiographs show fragmented epiphyses, widened metaphyses, and platyspondyly with anterior tongue-like projections. What is the most likely genetic etiology?

Explanation

Pseudoachondroplasia presents with severely affected epiphyses and metaphyses but normal craniofacial features, distinguishing it from classic achondroplasia. It is caused by mutations in the COMP (Cartilage Oligomeric Matrix Protein) gene.

Question 73

A newborn female is noted to have asymmetric limb shortening, ichthyosiform skin lesions, and cataracts. Radiographs demonstrate stippled, calcific deposits scattered throughout the epiphyses of the long bones and the spine. This condition is most strongly associated with a defect in which of the following pathways?

Explanation

Conradi-Hünermann-Happle syndrome (X-linked dominant chondrodysplasia punctata) is caused by mutations in the EBP gene, leading to defects in cholesterol biosynthesis. It characteristically presents with asymmetric limb shortening, cataracts, ichthyosis, and epiphyseal stippling.

Question 74

A 2-year-old boy presents with short trunk dwarfism, prominent stiff joints, a repaired cleft palate, and severe myopia. Radiographs reveal coronal clefts of the vertebral bodies, broad metaphyses, and prominent 'dumbbell-shaped' femora. Which of the following genes is most likely mutated?

Explanation

Kniest dysplasia is a type II collagenopathy caused by mutations in the COL2A1 gene. It is clinically characterized by severe myopia, cleft palate, short trunk dwarfism, and classic radiographic findings of dumbbell-shaped femora and coronal clefts in the vertebrae.

Question 75

A 2-year-old boy is brought in for a mild waddling gait. Radiographs show delayed, irregular ossification of both capital femoral epiphyses without metaphyseal cysts, subchondral fractures, or acetabular abnormalities. The spine is unaffected. By age 5, follow-up radiographs show near-complete resolution. What is the most likely diagnosis?

Explanation

Meyer dysplasia is a self-limiting condition characterized by delayed and irregular ossification of the capital femoral epiphysis, typically presenting around age 2. Unlike Legg-Calvé-Perthes disease, it lacks metaphyseal cysts or subchondral fractures and normalizes without surgical intervention.

Question 76

A 16-year-old girl presents with progressive, bilateral hip and knee pain. She has a history of sensorineural hearing loss, a repaired cleft palate, and a previous retinal detachment. Radiographs show mild epiphyseal flattening and early joint space narrowing in the hips and knees. This patient's syndrome is due to a mutation in which of the following structural proteins?

Explanation

Stickler syndrome is a connective tissue disorder typically caused by mutations in the COL2A1 or COL11A1 genes (Type II and XI collagen). It presents with mild spondyloepiphyseal dysplasia, early-onset osteoarthritis, retinal detachment, hearing loss, and Pierre Robin sequence.

Question 77

A 10-year-old girl is evaluated for sparse hair, a bulbous pear-shaped nose, and shortened fingers. Hand radiographs demonstrate prominent cone-shaped epiphyses in the middle phalanges. A mutation in which of the following genes is most likely responsible for this specific epiphyseal anomaly?

Explanation

Trichorhinophalangeal syndrome (TRPS) is characterized by sparse hair, a bulbous nasal tip, and characteristic cone-shaped epiphyses in the hands. It is caused by mutations in the TRPS1 gene, which encodes a zinc-finger transcription factor.

Question 78

A newborn presents with short-limbed dwarfism, bilateral rigid clubfeet, 'hitchhiker' thumbs, and cystic swelling of the external ears (cauliflower ears). Radiographs reveal severe epiphyseal dysplasia and progressive scoliosis. What is the molecular basis of this condition?

Explanation

Diastrophic dysplasia is an autosomal recessive condition caused by mutations in the SLC26A2 gene, resulting in defective intracellular sulfate transport. Clinical hallmarks include hitchhiker thumbs, cauliflower ears, rigid clubfeet, and severe epiphyseal dysplasia.

Question 79

A 5-year-old boy presents with an asymmetric, painless mass on the medial aspect of his right ankle. Radiographs reveal an osteochondroma-like cartilaginous overgrowth arising directly from the epiphysis of the distal tibia. Which of the following is the most appropriate initial management for this asymptomatic lesion?

Explanation

This presentation is classic for Dysplasia Epiphysealis Hemimelica (Trevor disease), a benign developmental anomaly of the epiphysis. Observation is the standard of care for asymptomatic lesions, with surgical excision reserved for cases causing pain, mechanical block, or progressive deformity.

Question 80

A 4-year-old child with a disproportionately short trunk, a flat facial profile, and high myopia presents for evaluation. Radiographs show delayed ossification of the pubic bones and flattened vertebral bodies. Prior to undergoing general anesthesia for an unrelated surgery, which of the following is the most critical screening study?

Explanation

This child has Spondyloepiphyseal Dysplasia Congenita (SEDC), caused by a COL2A1 mutation. Odontoid hypoplasia is common in SEDC, making flexion-extension cervical radiographs critical to rule out atlantoaxial instability before intubation.

Question 81

A 6-year-old girl presents with short stature, a waddling gait, and joint hyperlaxity. Her facial features and head circumference are completely normal. Radiographs reveal irregular epiphyses, widened metaphyses, and spatulate ribs. A mutation in the gene encoding which of the following proteins is most likely responsible?

Explanation

The clinical picture describes pseudoachondroplasia, which uniquely spares the craniofacies unlike achondroplasia. It is caused by mutations in the COMP gene, leading to accumulation of misfolded proteins in the rough endoplasmic reticulum of chondrocytes.

Question 82

A 9-year-old girl presents with bilateral hip stiffness and a waddling gait. Radiographs show delayed ossification and flattening of the capital femoral epiphyses. Which of the following radiographic features best distinguishes Multiple Epiphyseal Dysplasia (MED) from bilateral Legg-Calve-Perthes disease?

Explanation

MED typically presents with highly symmetrical bilateral epiphyseal changes. In contrast, bilateral Legg-Calve-Perthes disease is almost always asynchronous, presenting in varying stages of necrosis and healing between the two hips.

Question 83

A newborn is evaluated for asymmetrical shortening of the limbs, severe ichthyosis, and congenital cataracts. Radiographs demonstrate stippled calcifications within the epiphyses of the long bones and the spine. What is the inheritance pattern of the Conradi-Hunermann type of this disorder?

Explanation

Conradi-Hunermann syndrome is the X-linked dominant form of Chondrodysplasia Punctata, caused by mutations in the EBP gene. It is typically lethal in males and presents in females with asymmetric limb shortening, stippled epiphyses, and ichthyosis.

Question 84

A 2-year-old boy undergoes a pelvic radiograph for an unrelated abdominal complaint. The images incidentally reveal bilateral, multi-centric, granular ossification centers of the capital femoral epiphyses. He has a normal height and no pain. What is the most appropriate management?

Explanation

This is characteristic of Meyer dysplasia (dysplasia epiphysealis capitis femoris), a benign, self-limiting condition of delayed femoral head ossification. It is often an incidental finding and spontaneously resolves by 5 to 6 years of age without intervention.

Question 85

A 12-year-old boy presents with progressive hip pain and back stiffness. Physical exam reveals a disproportionately short trunk. Radiographs reveal platyspondyly with a characteristic hump-shaped buildup of bone on the central and posterior portions of the vertebral endplates. This condition is most commonly linked to a mutation in which of the following?

Explanation

The patient has Spondyloepiphyseal Dysplasia (SED) tarda, characterized by onset in late childhood and hump-shaped vertebral endplates. It is inherited in an X-linked recessive pattern due to mutations in the TRAPPC2 (sedlin) gene.

Question 86

A 7-year-old boy with a known history of Dysplasia Epiphysealis Hemimelica (Trevor disease) involving the medial aspect of his right knee is seen for follow-up. The parents are highly anxious about the potential for the cartilaginous lesion to become cancerous. What is the estimated risk of malignant transformation of this lesion?

Explanation

Dysplasia Epiphysealis Hemimelica is a benign developmental disorder of the epiphysis. Unlike osteochondromas, there are no documented cases of malignant transformation to chondrosarcoma in Trevor disease.

Question 87

A 35-year-old male with a documented history of Multiple Epiphyseal Dysplasia (MED) presents with progressive, severe joint pain. He has symmetrical involvement of his shoulders, hips, and knees. Which joint is most likely to require the earliest arthroplasty in the natural history of this condition?

Explanation

Early-onset osteoarthritis of the hips is the most debilitating complication of Multiple Epiphyseal Dysplasia. More than 50% of these patients require total hip arthroplasty, often at a relatively young age.

Question 88

A newborn presents with short-limb dwarfism, characteristic hitchhiker thumbs, bilateral rigid clubfeet, and cystic swelling of the external ears (cauliflower ears). Which of the following gene mutations is most directly responsible for this epiphyseal dysplasia variant?

Explanation

The clinical presentation is classic for Diastrophic Dysplasia. It is caused by an autosomal recessive mutation in the SLC26A2 gene, which encodes a sulfate transporter crucial for cartilage matrix formation.

Question 89

A 3-year-old boy is diagnosed with Spondyloepiphyseal Dysplasia Congenita (SEDC). Due to the systemic manifestations of the underlying collagen defect, he is referred for specialized evaluation. Which of the following is the most critical non-orthopedic screening required for this patient?

Explanation

SEDC is caused by a type II collagen (COL2A1) mutation, which affects both hyaline cartilage and the vitreous humor of the eye. Patients are at exceptionally high risk for severe myopia and retinal detachment, necessitating regular ophthalmologic screening.

Question 90

Dysplasia Epiphysealis Hemimelica (Trevor disease) is characterized by an asymmetric cartilage overgrowth that histologically resembles an osteochondroma. Which of the following is the most common anatomical location for this lesion?

Explanation

Trevor disease predominantly affects the lower extremities, most frequently involving the medial side of the epiphyses at the knee (distal femur) and the ankle (talus or distal tibia).

Question 91

A child is evaluated for short stature and skeletal deformities, and the differential diagnosis includes Spondyloepiphyseal Dysplasia Congenita (SEDC) and Pseudoachondroplasia. Which of the following clinical timelines best distinguishes pseudoachondroplasia from SEDC?

Explanation

Pseudoachondroplasia typically presents with a normal birth length and physical appearance, with growth retardation and waddling gait becoming evident around 2 to 3 years of age. SEDC, in contrast, is clinically apparent at birth.

Question 92

A newborn girl is noted to have stippled epiphyses on radiographs, nasal hypoplasia, and short distal phalanges. Her mother was treated for a chronic medical condition throughout her pregnancy. Maternal use of which of the following medications most likely caused this phenocopy of chondrodysplasia punctata?

Explanation

Warfarin is a known teratogen that inhibits vitamin K-dependent bone proteins like osteocalcin. Fetal warfarin syndrome clinically and radiographically mimics the stippled epiphyses and nasal hypoplasia seen in chondrodysplasia punctata.

Question 93

A 9-year-old boy presents with sparse hair, a bulbous pear-shaped nose, and mild short stature. Radiographs of the hands demonstrate distinct cone-shaped epiphyses in the phalanges. Which of the following is the most likely diagnosis?

Explanation

Trichorhinophalangeal syndrome (TRPS) is characterized by sparse hair, a bulbous nose, and cone-shaped epiphyses in the hands. It is an important epiphyseal dysplasia to recognize due to its highly specific radiographic and facial features.

Question 94

A 5-year-old boy presents with mild epiphyseal changes on radiographs, a cleft palate, micrognathia, and severe myopia. He has a history of early-onset hearing loss and hypermobile joints. Which of the following conditions is the most likely diagnosis?

Explanation

Stickler syndrome is a collagenopathy (often COL2A1) presenting with Pierre Robin sequence (cleft palate, micrognathia), epiphyseal dysplasia, eye abnormalities (myopia), and sensorineural hearing loss.

Question 95

A 3-year-old presents with a short trunk, prominent joints, and a flat midface. Radiographs reveal coronal clefts in the vertebral bodies and broad, dumbbell-shaped metaphyses with severely delayed epiphyseal ossification. Which of the following is the most likely diagnosis?

Explanation

Kniest dysplasia is a type II collagen disorder characterized by dumbbell-shaped femora, coronal clefts in the vertebrae, severe platyspondyly, and prominent, stiff joints. The presence of coronal clefts is a highly specific radiographic hallmark.

Question 96

A 4-year-old boy with disproportionate short-trunk dwarfism presents for orthopedic evaluation. He has a history of cleft palate and severe myopia. Radiographs reveal delayed ossification of the capital femoral epiphyses, severe coxa vara, and flattened, pear-shaped vertebral bodies. Prior to any surgical intervention requiring general anesthesia, flexion-extension radiographs of the cervical spine must be obtained to rule out atlantoaxial instability. This patient's condition is caused by a mutation affecting which of the following proteins?

Explanation

Spondyloepiphyseal dysplasia congenita (SEDC) is an autosomal dominant disorder caused by a mutation in the COL2A1 gene, which encodes Type II collagen. Classic features include short-trunk dwarfism, myopia, cleft palate, coxa vara, and a high risk of atlantoaxial instability, making cervical spine clearance mandatory before anesthesia.

Question 97

A 13-year-old boy presents with progressive back pain, hip stiffness, and a halting gait. Examination reveals a short trunk with an increased anteroposterior chest diameter (barrel chest). Radiographs of the lumbar spine demonstrate generalized platyspondyly with distinctive, hump-shaped central accumulations of bone on the posterior portions of the superior and inferior vertebral endplates. What is the inheritance pattern and most likely mutated gene associated with this patient's condition?

Explanation

This presentation is pathognomonic for X-linked Spondyloepiphyseal Dysplasia Tarda (SED tarda), characterized by the late-childhood onset of back/hip pain and 'hump-shaped' vertebral endplates. It is inherited in an X-linked recessive pattern and is caused by mutations in the TRAPPC2 gene (formerly SEDL), which encodes the protein sedlin.

Pediatric Orthopaedics: Comprehensive MCQ Question Bank & Exam Prep

Epiphyseal Skeletal Dysplasias MCQs | Ortho Board Review

Epiphyseal Skeletal Dysplasias MCQs | Ortho Board Review

Chapter Index