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4. Pediatrics MCQs

Practice Set 297 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 5921

Topic: Pediatric Upper Extremity & Spine

A 6-year-old girl sustains an extension-type supracondylar humerus fracture. Which of the following physical examination findings is most indicative of the most common nerve injury associated with this fracture pattern?

. Inability to extend the metacarpophalangeal joints
. Inability to flex the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger
. Decreased sensation over the dorsal first web space
. Weakness of the dorsal interossei
. Inability to cross the index and middle fingers

Correct Answer & Explanation

. Inability to flex the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger

Explanation

Correct Answer: BThe anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type supracondylar humerus fractures. It is a motor branch of the median nerve that innervates the flexor pollicis longus, the flexor digitorum profundus to the index and middle fingers, and the pronator quadratus. Injury results in the inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (making an 'A-OK' sign). Most of these injuries represent a neurapraxia and resolve spontaneously without surgical intervention.

Question 5922

Topic: Pediatric Hip

A 12-year-old boy with a BMI in the 98th percentile presents with 3 weeks of insidious onset left groin pain and a limp. Radiographs confirm a mild slipped capital femoral epiphysis (SCFE). What is the most appropriate initial management?

. Spica cast immobilization
. Closed reduction and percutaneous pinning
. In situ single screw fixation
. Open reduction and surgical subluxation
. Observation and non-weight-bearing with crutches

Correct Answer & Explanation

. In situ single screw fixation

Explanation

The standard of care for a stable, mild to moderate SCFE is in situ single screw fixation using a fully threaded screw to promote physeal closure and prevent further slippage. Closed reduction increases the risk of avascular necrosis and is generally contraindicated.

Question 5923

Topic: Pediatric Hip

A 6-week-old female infant with an irreducible developmental dysplasia of the hip (DDH) is placed in a Pavlik harness. After 3 weeks of strict, full-time wear, an ultrasound shows the hip remains completely dislocated. What is the next most appropriate step in management?

. Continue the Pavlik harness for an additional 3 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld splint)
. Immediate closed reduction and spica casting
. Immediate open reduction and spica casting
. Discontinue treatment and observe until 6 months of age for surgical intervention

Correct Answer & Explanation

. Transition to a rigid abduction orthosis (e.g., Ilfeld splint)

Explanation

If a Pavlik harness fails to achieve reduction after 3 to 4 weeks, it should be discontinued to prevent "Pavlik harness disease" (damage to the posterior acetabular lip). Transitioning to a rigid abduction orthosis is the standard next step before considering closed reduction under anesthesia.

Question 5924

Topic: 4. Pediatrics
A 4-year-old child presents with severe progressive deformity of the lower extremities, profound short stature, and dentinogenesis imperfecta. Radiographs of the knees show "popcorn" calcifications at the metaphyses. Which type of osteogenesis imperfecta does this patient most likely have?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type III

Explanation

Type III Osteogenesis Imperfecta is the most severe non-lethal form, characterized by progressive deformity, extreme short stature, and dentinogenesis imperfecta. Popcorn calcifications in the metaphyses are a classic radiographic hallmark seen in these severe cases.

Question 5925

Topic: 4. Pediatrics

A 6-year-old boy presents with a short trunk, barrel chest, and coxa vara. He has normal intelligence but exhibits a waddling gait. Radiographs show flattened vertebral bodies (platyspondyly) and delayed epiphyseal ossification. Genetic testing reveals a mutation in COL2A1. Which condition is most likely?

. Achondroplasia
. Pseudoachondroplasia
. Spondyloepiphyseal dysplasia congenita (SEDC)
. Multiple epiphyseal dysplasia
. Diastrophic dysplasia

Correct Answer & Explanation

. Spondyloepiphyseal dysplasia congenita (SEDC)

Explanation

Spondyloepiphyseal dysplasia congenita (SEDC) is a type II collagenopathy resulting from a COL2A1 mutation. Because type II collagen is prevalent in articular cartilage and the nucleus pulposus, patients display short-trunk dwarfism, significant spinal involvement, and epiphyseal dysplasia.

Question 5926

Topic: 4. Pediatrics

A newborn is evaluated for severe bilateral, rigid clubfeet. Physical examination reveals disproportionately short limbs, "hitchhiker" thumbs, and cystic swelling of the external ear bilaterally. Which of the following genes is mutated in this condition?

. COL1A1
. COMP
. FGFR3
. SLC26A2
. RUNX2

Correct Answer & Explanation

. SLC26A2

Explanation

The clinical picture of hitchhiker thumbs, cauliflower ears, and severe rigid clubfeet is diagnostic of diastrophic dysplasia. This condition is caused by a mutation in the SLC26A2 gene, which encodes a critical sulfate transporter.

Question 5927

Topic: 4. Pediatrics

A 5-year-old child presents with disproportionate short-limb dwarfism that was recognized only after he began walking. His facial features and head circumference are entirely normal. Radiographs show delayed epiphyseal ossification and anterior tongue-like projections of the vertebral bodies. Which gene is most likely mutated?

. COL2A1
. FGFR3
. COMP
. SLC26A2
. SOX9

Correct Answer & Explanation

. COMP

Explanation

Pseudoachondroplasia is caused by a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene. Unlike true achondroplasia, these patients have normal facial features and head size, and their short stature becomes apparent only in early childhood.

Question 5928

Topic: 4. Pediatrics

A 6-year-old boy with Osteogenesis Imperfecta presents with recurrent femoral fractures and severe progressive anterolateral bowing.

What is the surgical treatment of choice to manage the deformity and prevent fractures while allowing for continued longitudinal growth?

. Open reduction and rigid compression plate fixation
. Application of a multi-planar circular external fixator
. Standard non-elongating intramedullary nailing
. Telescoping intramedullary rodding (e.g., Fassier-Duval)
. Repeated percutaneous osteotomies followed by spica casting

Correct Answer & Explanation

. Telescoping intramedullary rodding (e.g., Fassier-Duval)

Explanation

Telescoping intramedullary rods are the gold standard for long bone deformity correction and fracture prevention in growing children with severe Osteogenesis Imperfecta. They expand with patient growth, reducing the need for frequent surgical rod revisions.

Question 5929

Topic: 4. Pediatrics

A 4-year-old boy presents with a history of recurrent fractures after minimal trauma, blue sclerae, and hearing loss.

Which of the following best describes the underlying genetic defect in the most common form of this condition?

. Autosomal dominant defect in the COL1A1 or COL1A2 gene
. Activating mutation in the FGFR3 gene
. Mutation in the COMP gene
. Autosomal recessive mutation in the RUNX2 (CBFA1) gene
. Defect in the diastrophic dysplasia sulfate transporter (DTDST)

Correct Answer & Explanation

. Autosomal dominant defect in the COL1A1 or COL1A2 gene

Explanation

Osteogenesis imperfecta (Type I) is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes. This leads to a quantitative defect (decreased production) of structurally normal type I collagen.

Question 5930

Topic: Pediatric Hip

In addition to hypoplastic or absent clavicles, which of the following is a classic radiographic finding associated with cleidocranial dysplasia?

. Coxa valga
. Premature closure of cranial sutures
. Widened symphysis pubis
. Acetabular protrusio
. Erlenmeyer flask deformity of the distal femur

Correct Answer & Explanation

. Widened symphysis pubis

Explanation

Cleidocranial dysplasia is associated with delayed ossification of midline structures. Classic findings include a widened symphysis pubis, delayed closure of cranial sutures (with wormian bones), and coxa vara.

Question 5931

Topic: 4. Pediatrics
According to the Sillence classification for Osteogenesis Imperfecta, which type is characterized as uniformly lethal in the perinatal period?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

Sillence Type II Osteogenesis Imperfecta is the most severe form. It is uniformly lethal in the perinatal period, typically due to severe pulmonary hypoplasia and multiple in-utero rib fractures.

Question 5932

Topic: 4. Pediatrics

A neonate is diagnosed with the most common form of short-limb dwarfism. Both parents are of normal height and stature. Which of the following describes the most likely genetic mutation and its mode of inheritance?

. COL2A1 mutation, autosomal recessive
. FGFR3 mutation, autosomal dominant
. COMP mutation, autosomal dominant
. CBFA1 mutation, autosomal dominant
. DTDST mutation, autosomal recessive

Correct Answer & Explanation

. FGFR3 mutation, autosomal dominant

Explanation

Achondroplasia is caused by an activating mutation in the FGFR3 gene, inherited in an autosomal dominant pattern. Approximately 80% of cases are spontaneous de novo mutations strongly associated with advanced paternal age.

Question 5933

Topic: 4. Pediatrics
A 7-year-old boy with Sillence Type III Osteogenesis Imperfecta presents with progressive anterolateral bowing of the femur. You elect to perform multiple osteotomies and intramedullary fixation. What is the primary biomechanical advantage of using a telescoping rod (e.g., Fassier-Duval) compared to a standard static intramedullary rod?
. Provides rigid rotational control
. Allows for continued longitudinal bone growth without the rod migrating into the diaphysis
. Promotes primary bone healing across the osteotomy sites
. Eliminates the need for postoperative bisphosphonate therapy
. Prevents the development of coxa vara

Correct Answer & Explanation

. Allows for continued longitudinal bone growth without the rod migrating into the diaphysis

Explanation

Telescoping rods, such as the Fassier-Duval rod, are anchored in the proximal and distal epiphyses. They elongate as the child grows, thereby protecting the entire length of the bone and preventing the rod from being outgrown or migrating.

Question 5934

Topic: 4. Pediatrics

A 4-year-old boy presents with a history of recurrent fractures after minimal trauma. Clinical exam reveals blue sclerae and opalescent teeth. Radiographs show generalized osteopenia and anterior bowing of the tibiae.

What is the underlying molecular defect in this patient's condition?

. Defect in type II collagen synthesis
. Defect in type I collagen synthesis
. Gain of function in FGFR3 receptor
. Defect in CBFA1 transcription factor
. Defect in COMP gene

Correct Answer & Explanation

. Defect in type I collagen synthesis

Explanation

Osteogenesis imperfecta is primarily caused by a qualitative or quantitative defect in type I collagen. This typically results from autosomal dominant mutations in the COL1A1 or COL1A2 genes.

Question 5935

Topic: 4. Pediatrics

A 3-year-old child presents with disproportionate short stature, rhizomelic shortening, and frontal bossing. The parents are of average height. Which of the following best describes the pathogenesis of the child's most likely condition?

. Loss of function mutation in FGFR3
. Gain of function mutation in FGFR3
. Defect in type I collagen synthesis
. Impaired sulfation of proteoglycans
. Defect in cartilage oligomeric matrix protein

Correct Answer & Explanation

. Gain of function mutation in FGFR3

Explanation

Achondroplasia is caused by an autosomal dominant, gain-of-function mutation in the FGFR3 gene. This overactive receptor inappropriately inhibits chondrocyte proliferation in the proliferative zone of the physis.

Question 5936

Topic: 4. Pediatrics

A 4-year-old boy presents with multiple recurrent fractures, blue sclerae, and hearing loss. Radiographs reveal generalized osteopenia and thin cortices.

What is the primary underlying biochemical defect in this condition?

. Defective synthesis of Type II collagen
. Quantitative or qualitative defect in Type I collagen
. Mutation in the FGFR3 gene
. Defect in cartilage oligomeric matrix protein (COMP)
. Defect in tissue-nonspecific alkaline phosphatase

Correct Answer & Explanation

. Quantitative or qualitative defect in Type I collagen

Explanation

Osteogenesis imperfecta is most commonly caused by mutations in the COL1A1 or COL1A2 genes, leading to defective Type I collagen. This results in bone fragility, blue sclerae, and dentinogenesis imperfecta.

Question 5937

Topic: 4. Pediatrics

A 5-year-old child presents with disproportionate short stature, rhizomelic shortening, and a prominent forehead. The genetic mutation responsible for this condition primarily affects which zone of the physis?

. Reserve (resting) zone
. Proliferative zone
. Hypertrophic zone
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Proliferative zone

Explanation

Achondroplasia is caused by a gain-of-function mutation in FGFR3, which inhibits chondrocyte proliferation. This defect primarily impairs the proliferative zone of the physis.

Question 5938

Topic: 4. Pediatrics

A 9-year-old boy presents with bilateral knee and hip pain, and a waddling gait. Radiographs demonstrate delayed, irregular, and fragmented ossification centers of the femoral heads and knees, while the spine is completely normal. Mutations in which of the following genes are most commonly associated with this condition?

. COL1A1
. COL2A1
. COMP
. FGFR3
. SOX9

Correct Answer & Explanation

. COMP

Explanation

Multiple Epiphyseal Dysplasia (MED) spares the spine and typically presents with fragmented epiphyses. It is most commonly associated with a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene.

Question 5939

Topic: Pediatric Hip

A 15-year-old boy presents for evaluation of delayed dental eruption. Examination reveals open skull sutures and absent clavicles.

Which of the following associated orthopedic conditions should also be screened for in this patient?

. Coxa vara
. Atlantoaxial instability
. Radial head dislocation
. Slipped capital femoral epiphysis
. Tibia vara

Correct Answer & Explanation

. Coxa vara

Explanation

Patients with cleidocranial dysplasia frequently develop coxa vara and scoliosis. Screening for these orthopedic manifestations is standard in managing the condition.

Question 5940

Topic: 4. Pediatrics
A neonate is born with severe extremity deformities, blue sclerae, and a soft skull. Radiographs show crumpled long bones, beaded ribs, and multiple fractures. The infant dies shortly after birth due to respiratory failure. Which Sillence classification type of osteogenesis imperfecta does this patient have?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

Sillence Type II is the perinatal lethal form of osteogenesis imperfecta. It is characterized by severe in utero fractures, 'crumpled' bones, and death usually due to pulmonary hypoplasia.

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