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4. Pediatrics MCQs

Practice Set 301 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 6001

Topic: 4. Pediatrics

A 4-year-old boy with spastic diplegic cerebral palsy presents with a severe scissoring gait. He has hyperreflexia and clonus in the lower extremities. He is able to sit only when supporting his trunk with his hands. Radiographs of the pelvis are obtained. Which of the following radiographic parameters is the most critical to monitor in this patient to determine the need for prophylactic adductor release?

. Acetabular index
. Reimers' migration index
. Center-edge angle of Wiberg
. Neck-shaft angle
. Alpha angle

Correct Answer & Explanation

. Reimers' migration index

Explanation

Correct Answer: BHip displacement is a common and severe complication in children with cerebral palsy, particularly those with higher Gross Motor Function Classification System (GMFCS) levels. Reimers' migration index (MI) is the standard radiographic measurement used in hip surveillance programs for children with CP. It measures the percentage of the femoral head that is lateral to Perkins' line. An MI greater than 30% indicates hip subluxation and is a trigger for closer monitoring or prophylactic soft tissue releases, such as adductor and iliopsoas tenotomies, to prevent further displacement. An MI greater than 50% typically requires bony reconstructive surgery, including a varus derotational osteotomy (VDRO) of the proximal femur and a pelvic osteotomy.

Question 6002

Topic: 4. Pediatrics

A 4-year-old boy with spastic diplegia is being evaluated for spasticity management. He exhibits severe scissoring when supported in a standing position. He requires his hands to support his trunk while sitting. Which of the following is the primary reason this patient is a poor candidate for selective dorsal rhizotomy (SDR)?

. Age of the patient
. Diagnosis of spastic diplegia
. Poor trunk control
. Presence of lower extremity clonus
. Near normal upper extremity function

Correct Answer & Explanation

. Poor trunk control

Explanation

Correct Answer: CSelective dorsal rhizotomy (SDR) is a neurosurgical procedure that involves sectioning a portion of the sensory nerve rootlets in the lower spinal cord to reduce spasticity in patients with cerebral palsy. Ideal candidates for SDR are children aged 3 to 8 years with spastic diplegia, good cognitive function, independent ambulation or the potential for it, and excellent underlying muscle strength and trunk control. The patient in this vignette requires his hands to support his trunk while sitting, indicating poor trunk control. Removing the spasticity in a patient who relies on it for truncal stability or standing can lead to a significant decline in functional status, making poor trunk control a major contraindication for SDR.

Question 6003

Topic: Pediatric Hip

A 12-year-old obese male presents with left knee pain and a limp. Radiographs confirm a mild, stable slipped capital femoral epiphysis (SCFE) on the left. Which of the following is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Age greater than 14 years
. Presentation greater than 3 weeks from symptom onset
. Normal Body Mass Index (BMI)
. Concomitant diagnosis of hypothyroidism
. Grade 1 initial slip severity

Correct Answer & Explanation

. Concomitant diagnosis of hypothyroidism

Explanation

Endocrine disorders (such as hypothyroidism or renal osteodystrophy) significantly increase the risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in these patients to prevent future displacement.

Question 6004

Topic: Pediatric Hip

A 4-month-old female is being treated in a Pavlik harness for developmental dysplasia of the hip (DDH). At her follow-up appointment, she demonstrates a loss of active knee extension on the affected side. What is the most likely cause of this finding?

. Obturator nerve palsy from excessive abduction
. Sciatic nerve palsy from excessive extension
. Peroneal nerve palsy from strap compression
. Femoral nerve palsy from excessive hip flexion
. Development of avascular necrosis of the femoral head

Correct Answer & Explanation

. Femoral nerve palsy from excessive hip flexion

Explanation

Femoral nerve palsy in a Pavlik harness is caused by excessive hip flexion. The harness should be adjusted or temporarily discontinued until nerve function recovers to prevent permanent deficits.

Question 6005

Topic: Pediatric Hip
An 8-year-old boy is diagnosed with Legg-Calvรฉ-Perthes disease. According to the Herring Lateral Pillar classification, which radiographic finding places the patient in the poorest prognostic group (Group C)?
. No involvement of the lateral pillar
. Greater than 50% of the lateral pillar height is maintained
. Less than 50% of the lateral pillar height is maintained
. Presence of a subchondral radiolucent line (crescent sign)
. Metaphyseal cysts without lateral pillar collapse

Correct Answer & Explanation

. Less than 50% of the lateral pillar height is maintained

Explanation

The Herring Lateral Pillar classification predicts the outcome of Perthes disease. Group C is defined by the maintenance of less than 50% of the original height of the lateral pillar and correlates with the worst long-term outcomes.

Question 6006

Topic: 4. Pediatrics

A 12-year-old obese boy presents with a 3-week history of knee pain and a limp. Examination shows his affected leg rests in external rotation. Radiographs demonstrate a widened physis, and Klein's line does not intersect the epiphysis. He is treated with in situ percutaneous pinning. What is the most common long-term complication of this condition?

. Chondrolysis
. Avascular necrosis of the femoral head
. Femoroacetabular impingement
. Hardware failure
. Premature physeal closure resulting in severe leg length discrepancy

Correct Answer & Explanation

. Femoroacetabular impingement

Explanation

Femoroacetabular impingement (FAI) is the most common long-term complication following slipped capital femoral epiphysis (SCFE). The residual prominent anterior metaphyseal bump leads to cam-type impingement against the acetabulum.

Question 6007

Topic: Pediatric Lower Extremity

A 2-week-old infant with idiopathic clubfoot is undergoing serial manipulation and casting using the Ponseti method. Which component of the deformity is corrected LAST during this sequence?

. Midfoot cavus
. Forefoot adductus
. Hindfoot varus
. Ankle equinus
. Forefoot supination

Correct Answer & Explanation

. Ankle equinus

Explanation

The Ponseti method follows a specific sequence of correction summarized by the acronym CAVE: Cavus, Adductus, Varus, and finally Equinus. Equinus is corrected last, often requiring a percutaneous Achilles tenotomy.

Question 6008

Topic: Pediatric Hip

A 6-month-old girl is evaluated for asymmetric gluteal folds. An AP pelvis radiograph demonstrates a right acetabular index of 35 degrees and a superolaterally displaced femoral head. What is the best initial management for this patient?

. Placement in a Pavlik harness
. Closed reduction and spica casting
. Open reduction and spica casting
. Femoral varus derotational osteotomy
. Observation with repeat radiographs in 3 months

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

For Developmental Dysplasia of the Hip (DDH) presenting in children aged 6 to 18 months, closed reduction and spica casting under general anesthesia is the standard initial treatment. The Pavlik harness has an unacceptably high failure rate in infants over 6 months of age.

Question 6009

Topic: Pediatric Hip

A 12-year-old boy presents to the emergency department with acute, severe groin pain and is completely unable to bear weight on his left leg. Radiographs reveal a severe left slipped capital femoral epiphysis (SCFE). Because he is unable to bear weight, he is classified as having an unstable SCFE. Which complication is he at highest risk for developing compared to a patient with a stable SCFE?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Contralateral slip progression
. Subtrochanteric femur fracture
. Septic arthritis

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

Unstable SCFE is defined by the inability to bear weight (with or without crutches) and carries a significantly higher risk of avascular necrosis (up to 47%) compared to stable SCFE. Urgent decompression and stabilization are prioritized to mitigate this devastating complication.

Question 6010

Topic: 4. Pediatrics

A 6-year-old boy presents with bilateral hip pain and a waddling gait. Radiographs show small, irregular, and fragmented epiphyses of the proximal femora. His father had early-onset hip osteoarthritis. Which gene is most commonly mutated in this condition?

. COMP
. COL2A1
. FGFR3
. CBFA1
. SOX9

Correct Answer & Explanation

. COMP

Explanation

Multiple Epiphyseal Dysplasia (MED) is most commonly caused by mutations in the COMP (Cartilage Oligomeric Matrix Protein) gene. It presents with delayed, irregular ossification of epiphyses and early-onset osteoarthritis.

Question 6011

Topic: 4. Pediatrics

A neonate presents with a cleft palate, bilateral clubfeet, and shortened limbs. Examination of the hands reveals a characteristic "hitchhiker thumb" deformity. What gene mutation is responsible for this condition?

. SLC26A2
. FGFR3
. COMP
. COL1A1
. GNAS1

Correct Answer & Explanation

. SLC26A2

Explanation

Diastrophic dysplasia is caused by a defect in the SLC26A2 sulfate transporter gene. It classically presents with rhizomelic shortening, cauliflower ears, hitchhiker thumbs, and severe, rigid clubfeet.

Question 6012

Topic: 4. Pediatrics
Which type of osteogenesis imperfecta is typically lethal in the perinatal period due to severe bone fragility, multiple intrauterine fractures, and respiratory failure?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

Osteogenesis imperfecta Type II is the most severe form and is uniformly lethal in the perinatal period, typically secondary to severe rib fractures, pulmonary hypoplasia, and subsequent respiratory failure.

Question 6013

Topic: 4. Pediatrics

A 6-year-old boy with short stature has a normal-appearing face, but shortened proximal limbs. Radiographs show delayed ossification of the epiphyses and irregular, fragmented metaphyses. Genetic testing reveals a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene. What is the most likely diagnosis?

. Achondroplasia
. Spondyloepiphyseal dysplasia congenita
. Pseudoachondroplasia
. Diastrophic dysplasia
. Cleidocranial dysplasia

Correct Answer & Explanation

. Pseudoachondroplasia

Explanation

Pseudoachondroplasia is caused by a COMP gene mutation. Unlike achondroplasia, these patients have normal craniofacial features at birth, and growth retardation generally becomes apparent around age 2.

Question 6014

Topic: Pediatric Hip

A 10-year-old girl is diagnosed with multiple epiphyseal dysplasia (MED). Radiographs of her knees are likely to demonstrate which of the following pathognomonic findings?

. Double-layer patella
. Stippled epiphyses
. Erlenmeyer flask deformity
. Coxa vara with a short femoral neck
. Hitchhiker thumb

Correct Answer & Explanation

. Double-layer patella

Explanation

A double-layer or multi-layered patella on a lateral knee radiograph is highly characteristic of Multiple Epiphyseal Dysplasia (MED). This condition typically spares the spine and facial structures, distinguishing it from spondyloepiphyseal dysplasia.

Question 6015

Topic: 4. Pediatrics

An 18-month-old male with achondroplasia presents with progressively worsening central sleep apnea and hyperreflexia. What is the most appropriate next step in management?

. Cervical spine flexion-extension radiographs
. MRI of the craniocervical junction
. Polysomnography alone
. Observation and repeat evaluation in 6 months
. Immediate posterior C1-C2 fusion

Correct Answer & Explanation

. MRI of the craniocervical junction

Explanation

Patients with achondroplasia (FGFR3 mutation) are at high risk for foramen magnum stenosis, which can cause cervicomedullary compression leading to central sleep apnea and hyperreflexia. Urgent MRI of the craniocervical junction is required to evaluate for surgical decompression.

Question 6016

Topic: 4. Pediatrics

A newborn is noted to have a "cauliflower" ear deformity, cleft palate, and a "hitchhiker" thumb. Radiographs reveal shortened first metacarpals and severe clubfeet. Which gene is most likely mutated in this patient?

. FGFR3
. SLC26A2
. COL2A1
. COL1A1
. RUNX2

Correct Answer & Explanation

. SLC26A2

Explanation

Diastrophic dysplasia is an autosomal recessive condition caused by a mutation in the SLC26A2 gene (diastrophic dysplasia sulfate transporter). Classic findings include hitchhiker thumbs, cauliflower ears, and rigid clubfeet.

Question 6017

Topic: 4. Pediatrics

A 4-year-old boy presents with disproportionate short stature, lumbar lordosis, and a waddling gait. His facial features are normal. Radiographs reveal severe coxa vara and delayed ossification of the capital femoral epiphyses. His spine shows platyspondyly. A mutation in which gene is most likely responsible?

. COL2A1
. FGFR3
. COMP
. SLC26A2
. SOX9

Correct Answer & Explanation

. COL2A1

Explanation

Spondyloepiphyseal dysplasia (SED) congenita is caused by a COL2A1 mutation. It affects type II collagen, predominantly involving the spine (platyspondyly) and epiphyses (severe coxa vara), while classically sparing the face.

Question 6018

Topic: Pediatric Hip

A 7-year-old child presents with retained deciduous teeth, delayed closure of cranial sutures, and hypermobility of the shoulders, allowing them to be brought together in the midline. Which of the following is the most common orthopedic manifestation requiring surgical intervention in this syndrome?

. Coxa vara
. Atlantoaxial instability
. Scoliosis
. Recurrent patellar dislocation
. Slipped capital femoral epiphysis

Correct Answer & Explanation

. Coxa vara

Explanation

Cleidocranial dysplasia is caused by a RUNX2 (CBFA1) mutation. While clavicular hypoplasia is classic, progressive coxa vara is the most common orthopedic issue requiring surgical intervention, often via a valgus-producing proximal femoral osteotomy.

Question 6019

Topic: 4. Pediatrics

A 9-month-old infant with achondroplasia is noted by his parents to have apneic episodes during sleep, excessive sweating, and generalized hypotonia. Which of the following diagnostic studies is most critical to perform next?

. Echocardiogram
. Polysomnography and MRI of the cervical spine/cervicomedullary junction
. Radiographs of the thoracolumbar spine
. Pulmonary function testing
. Genetic testing for FGFR3 mutation

Correct Answer & Explanation

. Polysomnography and MRI of the cervical spine/cervicomedullary junction

Explanation

Infants with achondroplasia are at high risk for cervicomedullary compression due to a stenotic foramen magnum, presenting as central sleep apnea, hypotonia, or sudden death. MRI and sleep studies are critical for prompt diagnosis and surgical decompression.

Question 6020

Topic: 4. Pediatrics

A newborn infant is noted to have severe short-limbed dwarfism, bilateral clubfeet, distinctive 'hitchhiker' thumbs, and cystic swelling of the external ears (cauliflower ears). Which of the following pathways is fundamentally disrupted in this patient's condition?

. Fibroblast growth factor receptor signaling
. Intracellular sulfate transport
. Type X collagen synthesis
. Cartilage oligomeric matrix protein secretion
. Carbonic anhydrase function

Correct Answer & Explanation

. Intracellular sulfate transport

Explanation

Diastrophic dysplasia is caused by an autosomal recessive mutation in the SLC26A2 (DTDST) gene, which encodes a sulfate transporter. Defective intracellular sulfate transport leads to undersulfated proteoglycans in the cartilage matrix.

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