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4. Pediatrics MCQs

Practice Set 12 of 334

This practice set contains high-yield board review questions covering key concepts in 4. Pediatrics. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 221

Topic: 4. Pediatrics

A newborn infant is noted to have short limbs, rigid clubfeet, cystic swelling of the ear pinnae (cauliflower ears), and proximally placed, abducted thumbs (hitchhiker thumbs). This condition is caused by a defect in which of the following?

. Sulfate transport (SLC26A2)
. Type 1 collagen synthesis
. Chondrocyte proliferation via FGFR3
. Cartilage oligomeric matrix protein
. Core binding factor alpha 1

Correct Answer & Explanation

. Sulfate transport (SLC26A2)

Explanation

Diastrophic dysplasia is an autosomal recessive disorder caused by a mutation in the SLC26A2 (DTDST) gene, leading to defective sulfate transport. Classic findings include hitchhiker thumbs, cauliflower ears, and rigid clubfeet.

Question 222

Topic: 4. Pediatrics

A 2-year-old child presents with an asymptomatic, painless mass over the mid-clavicle. There is no history of trauma. Radiographs reveal a defect in the middle third of the right clavicle with smooth, rounded bone ends. What is the most appropriate management?

. Immediate open reduction and internal fixation
. Spica cast immobilization
. Excision of the mass and bone grafting at age 3 to 5 years if symptomatic
. Shoulder hemiarthroplasty
. Observation, as it will spontaneously heal by skeletal maturity

Correct Answer & Explanation

. Excision of the mass and bone grafting at age 3 to 5 years if symptomatic

Explanation

Congenital pseudarthrosis of the clavicle almost always occurs on the right side and presents as a painless mass. Surgery is indicated if the patient is symptomatic, has skin compromise, or for cosmetic concerns, typically delayed until 3 to 5 years of age.

Question 223

Topic: 4. Pediatrics

A 4-year-old boy presents with progressive, asymmetric limb overgrowth, plantar cerebriform connective tissue nevi, and epidermal nevi. A mutation in which of the following genes is classically associated with this syndrome?

. AKT1
. NF1
. PTEN
. PIK3CA
. FGFR3

Correct Answer & Explanation

. AKT1

Explanation

The presentation is classic for Proteus syndrome, characterized by cerebriform connective tissue nevi, epidermal nevi, and asymmetric overgrowth. It is caused by a somatic mosaic mutation in the AKT1 gene.

Question 224

Topic: 4. Pediatrics

A 5-year-old boy has short-trunk dwarfism, coxa vara, and myopia. Radiographs reveal delayed ossification of the femoral heads and platyspondyly. Which of the following genetic mutations is responsible for this condition?

. COL1A1
. COL2A1
. FGFR3
. COMP
. CBFA1

Correct Answer & Explanation

. COL2A1

Explanation

Spondyloepiphyseal dysplasia (SED) congenita is caused by mutations in the COL2A1 gene encoding type II collagen. Clinical features include short-trunk dwarfism, coxa vara, myopia, and atlantoaxial instability.

Question 225

Topic: 4. Pediatrics
A 3-year-old child with multiple café-au-lait spots and axillary freckling presents with anterolateral bowing of the tibia. Radiographs show medullary canal narrowing and early pseudarthrosis. Which of the following is true regarding surgical management?
. Simple bone grafting alone has a high union rate.
. Intramedullary rodding and resection of the pseudarthrosis with bone grafting is the standard of care.
. Amputation is recommended as the first-line treatment.
. Plate fixation without bone grafting is sufficient.
. The pseudarthrosis usually heals spontaneously after age 5.

Correct Answer & Explanation

. Intramedullary rodding and resection of the pseudarthrosis with bone grafting is the standard of care.

Explanation

Congenital pseudarthrosis of the tibia is highly associated with NF1 and is notoriously difficult to treat. Standard surgical management involves aggressive resection of the hamartomatous tissue, intramedullary rodding, and robust bone grafting.

Question 226

Topic: 4. Pediatrics
A newborn is diagnosed with osteogenesis imperfecta. According to the Sillence classification, which type is characterized by normal or near-normal stature and blue sclerae throughout life, making it the most common and mildest form?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type I

Explanation

Sillence Type I is the most common and mildest form of OI, characterized by blue sclerae, recurrent fractures that decrease after puberty, and near-normal stature. Type II is perinatally lethal, and Type III is the most severe non-lethal form.

Question 227

Topic: 4. Pediatrics

A newborn presents with a deep constriction ring around the left lower leg and a distal clubfoot deformity. The toes exhibit acrosyndactyly. Which of the following is the most appropriate management for the deep constriction ring if it is causing distal vascular compromise?

. Observation and serial casting
. Surgical release via single-stage circumferential Z-plasty
. Surgical release via staged (two-stage) Z-plasties
. Immediate below-knee amputation
. Ilizarov lengthening

Correct Answer & Explanation

. Surgical release via staged (two-stage) Z-plasties

Explanation

Constriction bands in amniotic band syndrome that threaten limb viability require surgical excision. This is performed using staged Z-plasties (releasing 50% of the circumference at a time) to prevent vascular compromise to the distal limb.

Question 228

Topic: 4. Pediatrics

A 1-year-old girl is evaluated for a short right leg. Examination reveals an absent 5th ray, anteromedial bowing of the tibia, and a dimple over the anterior shin. Radiographs confirm complete absence of the fibula. Which of the following knee ligament anomalies is most commonly associated?

. Medial collateral ligament absence
. Cruciate ligament absence or hypoplasia
. Lateral collateral ligament duplication
. Patellar tendon rupture
. Posterior oblique ligament contracture

Correct Answer & Explanation

. Cruciate ligament absence or hypoplasia

Explanation

Fibular hemimelia is the most common congenital long bone deficiency. It is frequently associated with anteromedial bowing of the tibia, absence of lateral foot rays, and absent or hypoplastic anterior/posterior cruciate ligaments.

Question 229

Topic: Pediatric Lower Extremity

A child is born with a severely shortened right thigh held in flexion, abduction, and external rotation. Radiographs show absence of the proximal femur. According to the Aitken classification, a Type C Proximal Focal Femoral Deficiency (PFFD) is characterized by which of the following?

. Normal acetabulum with a short femur and bony connection to the femoral head
. Severe shortening with no acetabulum and no femoral head
. Dysplastic acetabulum, absent femoral head, and no bony connection
. Normal acetabulum and femoral head with a subtrochanteric pseudarthrosis
. Normal hip joint with isolated shortening of the femoral shaft

Correct Answer & Explanation

. Dysplastic acetabulum, absent femoral head, and no bony connection

Explanation

In Aitken Type C PFFD, the acetabulum is severely dysplastic, the femoral head is absent, and there is no connection between the shaft and the pelvis. Type D is the most severe, with no acetabulum or femoral head.

Question 230

Topic: 4. Pediatrics

A 2-year-old boy presents with short stature, frontal bossing, and rhizomelic shortening of the limbs. Genetic testing reveals a mutation in the FGFR3 gene. Which of the following is true regarding the pathophysiology and inheritance of this condition?

. Inheritance is strictly autosomal recessive
. Associated primarily with advanced maternal age
. The mutation causes a gain of function that inhibits chondrocyte proliferation
. It requires immediate bisphosphonate therapy to prevent fractures
. Cervical kyphosis typically requires surgical fusion in early infancy

Correct Answer & Explanation

. The mutation causes a gain of function that inhibits chondrocyte proliferation

Explanation

Achondroplasia is caused by a gain-of-function mutation in FGFR3, which abnormally inhibits chondrocyte proliferation at the physis. It is an autosomal dominant condition strongly associated with advanced paternal age.

Question 231

Topic: 4. Pediatrics

A newborn presents with micromelic shortening, severe rigid clubfeet, "hitchhiker" thumbs, and cauliflower ears. What is the most likely underlying genetic defect?

. COL1A1 gene mutation
. COMP gene mutation
. SLC26A2 (DTDST) gene mutation
. FGFR3 gene mutation
. SOX9 gene mutation

Correct Answer & Explanation

. SLC26A2 (DTDST) gene mutation

Explanation

Diastrophic dysplasia is an autosomal recessive disorder caused by a defect in the SLC26A2 (DTDST) gene, an essential sulfate transporter. Clinical hallmarks include hitchhiker thumbs, severe clubfeet, and auricular cysts.

Question 232

Topic: 4. Pediatrics

A 1-year-old child presents with a shortened right lower extremity. Radiographs reveal a severe proximal focal femoral deficiency (Aitken Class D) with absent hip joint.

Which of the following conditions is most frequently associated with this specific congenital anomaly?

. Fibular hemimelia
. Tibial hemimelia
. Radial clubhand
. Anencephaly
. Down syndrome

Correct Answer & Explanation

. Fibular hemimelia

Explanation

Proximal focal femoral deficiency (PFFD) has a very high association (up to 70-80%) with fibular hemimelia. Both anomalies are considered part of a spectrum of postaxial longitudinal deficiencies of the lower extremity.

Question 233

Topic: 4. Pediatrics

An infant is born with shortening of the leg, an anteromedial bow of the tibia, absent lateral rays of the foot, and a severe equinovalgus foot deformity. What is the most likely diagnosis?

. Tibial hemimelia
. Fibular hemimelia
. Congenital pseudarthrosis of the tibia
. Amniotic band sequence
. Proximal focal femoral deficiency

Correct Answer & Explanation

. Fibular hemimelia

Explanation

Fibular hemimelia is the most common longitudinal deficiency of the long bones. It classically presents with anteromedial bowing of the tibia, absent lateral rays of the foot, and an equinovalgus foot deformity.

Question 234

Topic: 4. Pediatrics

A 3-year-old child with anterolateral bowing of the tibia develops a fracture that fails to heal despite casting.

Which of the following systemic conditions is most strongly associated with this bony pathology?

. Achondroplasia
. Osteogenesis Imperfecta
. Neurofibromatosis type 1
. Fibrous Dysplasia
. Klippel-Trenaunay Syndrome

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Congenital pseudarthrosis of the tibia (CPT) with anterolateral bowing is highly associated with Neurofibromatosis type 1 (NF1). Up to 50% of patients with this specific tibial deformity have underlying NF1.

Question 235

Topic: 4. Pediatrics

A child with short-trunk dwarfism, a barrel chest, and coxa vara is diagnosed with Spondyloepiphyseal dysplasia congenita (SEDC). Which of the following genetic defects is characteristic of this disorder?

. Defect in type I collagen
. Defect in type II collagen
. Defect in type X collagen
. Defect in the COMP gene
. Defect in the FGFR3 gene

Correct Answer & Explanation

. Defect in type II collagen

Explanation

SED congenita is caused by mutations in the COL2A1 gene, resulting in defective type II collagen. This primarily affects hyaline cartilage, leading to short-trunk dwarfism, severe coxa vara, and an increased risk of retinal detachment.

Question 236

Topic: 4. Pediatrics

A 5-year-old boy presents with progressive, disproportionate overgrowth of the right lower extremity, macrodactyly, and cerebriform connective tissue nevi on his foot. The mutation associated with this syndrome is most likely located in which gene?

. AKT1
. FGFR3
. GNAS
. PIK3CA
. PTEN

Correct Answer & Explanation

. AKT1

Explanation

Proteus syndrome is a rare, sporadic overgrowth disorder caused by a somatic mosaic mutation in the AKT1 gene. It is clinically characterized by progressive, disproportionate overgrowth of limbs, bone abnormalities, and characteristic cerebriform connective tissue nevi.

Question 237

Topic: 4. Pediatrics

A 4-year-old child presents with short-limb dwarfism but was of normal length at birth. Radiographs show small, irregular epiphyses and fragmented metaphyses. The face and head are normal. Genetic testing shows a defect in the COMP gene. What is the diagnosis?

. Achondroplasia
. Multiple Epiphyseal Dysplasia
. Pseudoachondroplasia
. Diastrophic Dysplasia
. Spondyloepiphyseal Dysplasia

Correct Answer & Explanation

. Pseudoachondroplasia

Explanation

Pseudoachondroplasia presents with normal birth length, subsequent short-limb dwarfism, normal facies, and marked epiphyseal/metaphyseal irregularities. Like MED, it is caused by mutations in the COMP gene, but the clinical phenotype includes significant metaphyseal involvement and dwarfism.

Question 238

Topic: 4. Pediatrics

An infant is born with ring-like constrictions on multiple digits of both hands, and a severe clubfoot on the right side.

Which of the following is true regarding this syndrome?

. It has a 25% recurrence risk in subsequent pregnancies
. It is caused by an inherited autosomal dominant mutation
. The associated clubfoot is typically flexible and easy to correct with serial casting
. It is sporadic and occurs secondary to early amnion rupture
. It primarily affects the proximal segments of the limbs, sparing the digits

Correct Answer & Explanation

. It is sporadic and occurs secondary to early amnion rupture

Explanation

Congenital constriction band syndrome (amniotic band syndrome) is a sporadic, non-genetic condition resulting from in utero amnion rupture and entanglement of fetal parts. The associated clubfeet are often rigid, resistant to casting, and require surgical release.

Question 239

Topic: Pediatric Lower Extremity

A newborn is evaluated for a markedly shortened thigh and flexed, abducted, and externally rotated hip. Radiographs reveal absence of the proximal femur but a normal acetabulum. Which of the following conditions is most likely to be present ipsilaterally?

. Tibial hemimelia
. Fibular hemimelia
. Developmental dysplasia of the hip
. Blount disease
. Clubfoot

Correct Answer & Explanation

. Fibular hemimelia

Explanation

Proximal focal femoral deficiency (PFFD) is commonly associated with ipsilateral fibular hemimelia in up to 50-70% of cases. The acetabulum can range from normal to severely dysplastic depending on the Aitken classification.

Question 240

Topic: 4. Pediatrics

A mother brings her 3-month-old infant to the clinic because of a painless lump over the right collarbone. There is no history of birth trauma. Radiographs show a distinct lucency in the middle third of the right clavicle with smooth, rounded bone ends. What is the most appropriate management?

. Immediate open reduction and internal fixation
. Figure-of-eight brace
. Observation until age 3-4 followed by excision and bone grafting if symptomatic
. Genetic testing for neurofibromatosis
. Excision of the medial segment only

Correct Answer & Explanation

. Observation until age 3-4 followed by excision and bone grafting if symptomatic

Explanation

Congenital pseudarthrosis of the clavicle typically occurs on the right side and presents as a painless mass. Management is primarily observation; surgical repair with bone grafting is indicated if the patient is symptomatic or has significant cosmetic deformity, usually delayed until 3-5 years of age.

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