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4. Pediatrics MCQs

Practice Set 284 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 5661

Topic: Pediatric Hip

A 13-year-old obese boy presents with right knee pain and a limp. Examination reveals obligate external rotation of the right hip with passive flexion. Slipped Capital Femoral Epiphysis (SCFE) is diagnosed. What is the most common direction of displacement of the proximal femoral epiphysis relative to the femoral neck (metaphysis)?

. Anterior and Superior
. Anterior and Inferior
. Posterior and Superior
. Posterior and Inferior
. Directly Medial

Correct Answer & Explanation

. Posterior and Inferior

Explanation

In SCFE, the femoral neck (metaphysis) typically displaces anteriorly and superiorly relative to the epiphysis. Consequently, the epiphysis is anatomically described as being displaced posteriorly and inferiorly relative to the femoral neck.

Question 5662

Topic: 4. Pediatrics

A pediatric patient with frontal bossing, rhizomelic dwarfism, and a trident hand is evaluated. This condition is caused by a gain-of-function mutation in FGFR3. Which specific zone of the physis is primarily inhibited by this mutation?

. Reserve zone
. Proliferative zone
. Hypertrophic zone
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Proliferative zone

Explanation

The patient has achondroplasia. The gain-of-function mutation in Fibroblast Growth Factor Receptor 3 (FGFR3) abnormally inhibits chondrocyte proliferation, leading to a profound defect primarily in the proliferative zone of the physis.

Question 5663

Topic: 4. Pediatrics
A 4-year-old child with frequent fractures, blue sclerae, and dentinogenesis imperfecta is diagnosed with osteogenesis imperfecta. The severe, qualitative forms of this disease are most commonly caused by which of the following molecular defects?
. Substitution of glycine by a bulkier amino acid in the Type I collagen triple helix
. A quantitative null-allele mutation resulting in half the normal amount of normal Type I collagen
. Substitution of proline in the Type II collagen sequence
. A frameshift mutation in the COL10A1 gene
. A defect in the enzymatic cross-linking of mature collagen fibrils outside the cell

Correct Answer & Explanation

. Substitution of glycine by a bulkier amino acid in the Type I collagen triple helix

Explanation

Qualitative, more severe forms of osteogenesis imperfecta (e.g., Types II, III, IV) are typically caused by missense mutations that substitute a bulkier amino acid for glycine in the COL1A1 or COL1A2 genes. This disrupts the tight coiling of the Type I collagen triple helix. Mild OI (Type I) is usually due to a quantitative defect (null allele).

Question 5664

Topic: Pediatric Hip

Which of the following underlying conditions is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a 12-year-old patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. Obesity (>95th percentile for BMI)
. Male gender
. Renal osteodystrophy
. African American ethnicity
. Participation in high-impact sports

Correct Answer & Explanation

. Renal osteodystrophy

Explanation

Patients with endocrine or metabolic disorders, such as renal osteodystrophy or hypothyroidism, have a much higher risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly recommended in these atypical presentations.

Question 5665

Topic: Pediatric Hip

An infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the 2-week follow-up, the parents report the infant is no longer actively extending the knee on the treated side. This complication is most commonly associated with which of the following harness positioning errors?

. Excessive hip flexion
. Inadequate hip flexion
. Excessive hip abduction
. Inadequate hip abduction
. Excessive internal rotation

Correct Answer & Explanation

. Excessive hip flexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness and is typically caused by hyperflexion of the hip. In contrast, excessive hip abduction is famously associated with avascular necrosis of the femoral head.

Question 5666

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy sustains a completely displaced (Gartland type III) extension-type supracondylar humerus fracture. Upon initial evaluation, the hand is pink and well-perfused, but the radial pulse is entirely absent. What is the most appropriate next step in management?
. Immediate open exploration of the brachial artery
. Stat CT angiogram of the upper extremity
. Urgent closed reduction and percutaneous pinning, followed by vascular reassessment
. Application of a long arm cast in hyperflexion to restore the pulse
. Immediate fasciotomy of the forearm

Correct Answer & Explanation

. Urgent closed reduction and percutaneous pinning, followed by vascular reassessment

Explanation

For a 'pulseless, pink' hand following a supracondylar humerus fracture, collateral circulation is providing adequate perfusion. The most appropriate next step is urgent closed reduction and pinning, which unkinks the brachial artery and often restores the palpable pulse.

Question 5667

Topic: Pediatric Hip

A 12-year-old obese male presents with acute on chronic slipped capital femoral epiphysis (SCFE). What is the primary blood supply at risk of disruption during surgical pinning?

. Medial femoral circumflex artery
. Lateral femoral circumflex artery
. Ligamentum teres artery
. Inferior gluteal artery
. Superior gluteal artery

Correct Answer & Explanation

. Medial femoral circumflex artery

Explanation

The medial femoral circumflex artery (MFCA), specifically its posterosuperior retinacular branches, is the primary blood supply to the femoral head in this age group and is at high risk of injury in SCFE.

Question 5668

Topic: Pediatric Hip

A 3-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). Hyperflexion of the hip in the harness places the child at highest risk for which of the following complications?

. Femoral nerve palsy
. Sciatic nerve palsy
. Avascular necrosis of the femoral head
. Inferior hip dislocation
. Obturator nerve palsy

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Hyperflexion in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to an iatrogenic femoral nerve palsy. Excessive abduction, conversely, increases the risk of avascular necrosis.

Question 5669

Topic: Pediatric Hip

A 13-year-old overweight male presents with 3 weeks of vague knee pain and an antalgic limp. Examination reveals obligate external rotation of the hip with passive flexion. What is the most severe potential complication of the definitive surgical treatment for his condition?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Femoroacetabular impingement
. Slip progression
. Leg length discrepancy

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

The presentation is classic for a slipped capital femoral epiphysis (SCFE). While chondrolysis and impingement are known risks, AVN of the femoral head is the most severe and devastating complication associated with SCFE and surgical pinning.

Question 5670

Topic: 4. Pediatrics

A couple with normal stature has a child diagnosed with achondroplasia. They are concerned about the genetics of this condition and ask about the likelihood of this occurring. Based on the epidemiology of achondroplasia, what is the most accurate genetic explanation?

. Autosomal recessive inheritance from carrier parents
. X-linked recessive mutation inherited from the mother
. De novo mutation of a gene on chromosome 4
. Maternal chromosomal nondisjunction during meiosis
. De novo mutation of a gene on chromosome 21

Correct Answer & Explanation

. De novo mutation of a gene on chromosome 4

Explanation

Correct Answer: De novo mutation of a gene on chromosome 4Achondroplasia is inherited in an autosomal dominant manner. However, over 80% of individuals with achondroplasia have parents with normal stature. In these cases, the condition is the result of a 'de novo' (new) mutation of a gene localized to the distal short arm of chromosome 4.

Question 5671

Topic: 4. Pediatrics

A 4-year-old boy presents with delayed motor milestones and the facial features shown below. What is the most likely diagnosis?



. Osteogenesis Imperfecta
. Mucopolysaccharidosis
. Achondroplasia
. Spondyloepiphyseal dysplasia
. Cleidocranial dysplasia

Correct Answer & Explanation

. Achondroplasia

Explanation

Correct Answer: AchondroplasiaThe clinical image shows a child with a head that is disproportionately large in relation to height, a prominent forehead (frontal bossing), and a broadened, depressed nasal bridge. These are the hallmark craniofacial features of achondroplasia, the most common human chondrodysplasia.

Question 5672

Topic: 4. Pediatrics

An infant is diagnosed with achondroplasia shortly after birth. The parents are counseled regarding potential life-threatening complications during infancy. Which of the following represents the greatest risk of mortality in this age group?

. Severe restrictive lung disease from a narrow chest
. Congenital cardiac anomalies
. Spinal cord compression and upper airway obstruction
. Recurrent severe pulmonary infections due to immunodeficiency
. Malignant hyperthermia during anesthesia

Correct Answer & Explanation

. Spinal cord compression and upper airway obstruction

Explanation

Correct Answer: Spinal cord compression and upper airway obstructionIn infancy, patients with achondroplasia are at an increased risk of death primarily due to compression of the spinal cord (often at the foramen magnum) and upper airway obstruction.

Question 5673

Topic: 4. Pediatrics

A 12-month-old infant with achondroplasia is brought to the clinic. The parents are concerned because the child is not yet walking and seems 'floppy.' Which of the following is the most appropriate counseling regarding the child's development?

. Hypotonia and delayed motor milestones are typical, but intelligence is usually normal
. The delay is likely due to severe intellectual disability associated with the condition
. Immediate surgical decompression of the foramen magnum is required to restore motor function
. The child will likely never achieve independent ambulation due to the skeletal dysplasia
. Hypotonia indicates a concomitant muscular dystrophy requiring muscle biopsy

Correct Answer & Explanation

. Hypotonia and delayed motor milestones are typical, but intelligence is usually normal

Explanation

Correct Answer: Hypotonia and delayed motor milestones are typical, but intelligence is usually normalIn infancy, hypotonia is typical in achondroplasia, and the acquisition of developmental motor milestones is often delayed. However, intelligence and life span are usually normal, and parents should be reassured regarding cognitive development.

Question 5674

Topic: 4. Pediatrics

A 10-year-old girl with achondroplasia asks about her expected final adult height. According to established growth data for this condition, what is the mean adult height for females?

. 105 cm
. 115 cm
. 124 cm
. 131 cm
. 145 cm

Correct Answer & Explanation

. 124 cm

Explanation

Correct Answer: 124 cmAccording to the clinical data for achondroplasia, the mean adult height in males is 131 ± 5.6 cm, and in females, it is 124 ± 5.9 cm.

Question 5675

Topic: 4. Pediatrics

Achondroplasia is caused by a mutation that affects endochondral ossification. The responsible gene is localized to which of the following chromosomal regions?

. Distal short arm of chromosome 4
. Long arm of chromosome 15
. Short arm of chromosome X
. Long arm of chromosome 21
. Distal short arm of chromosome 17

Correct Answer & Explanation

. Distal short arm of chromosome 4

Explanation

Correct Answer: Distal short arm of chromosome 4Achondroplasia is the result of a mutation of a gene (FGFR3) localized to the distal short arm of chromosome 4. This mutation leads to a gain of function that inhibits chondrocyte proliferation, resulting in disproportionate short-limb dwarfism.

Question 5676

Topic: 4. Pediatrics

A child presents with the facial features shown below. Which of the following genetic mutations is most likely responsible for this phenotype?


. Mutation on the long arm of chromosome 15
. Mutation on the distal short arm of chromosome 4
. Mutation in the COL1A1 gene
. Mutation in the COMP gene
. Mutation in the RUNX2 gene

Correct Answer & Explanation

. Mutation on the distal short arm of chromosome 4

Explanation

Correct Answer: Mutation on the distal short arm of chromosome 4The clinical image demonstrates a disproportionately large head, prominent forehead, and a broadened, depressed nasal bridge typical of achondroplasia. This condition is caused by a mutation localized to the distal short arm of chromosome 4 (specifically the FGFR3 gene).

Question 5677

Topic: 4. Pediatrics

A patient with the condition shown below presents to the clinic. Which of the following joint findings is typically associated with this disorder?


. Limitation of elbow extension and rotation
. Severe limitation of knee extension
. Genu valgum deformity
. Decreased lumbar lordosis
. Global joint stiffness

Correct Answer & Explanation

. Limitation of elbow extension and rotation

Explanation

Correct Answer: Limitation of elbow extension and rotationPatients with achondroplasia typically exhibit exaggerated lumbar lordosis, genu varum, hyperextension of the knees and most other joints, but characteristically have a limitation of elbow extension and rotation.

Question 5678

Topic: 4. Pediatrics

A couple with normal stature has a child diagnosed with achondroplasia. They are concerned about the risk of having another child with the same condition. What percentage of achondroplasia cases are the result of a de novo mutation in parents with normal stature?

. Less than 10%
. Approximately 25%
. Approximately 50%
. Over 80%
. 100%

Correct Answer & Explanation

. Over 80%

Explanation

Correct Answer: Over 80%Over 80% of individuals with achondroplasia have parents with normal stature. In these cases, the condition is the result of a spontaneous 'de novo' mutation.

Question 5679

Topic: 4. Pediatrics

An infant is diagnosed with achondroplasia. Which of the following is a typical finding during the first year of life in this patient population?

. Hypertonia
. Accelerated acquisition of motor milestones
. Hypotonia and delayed motor milestones
. Severe intellectual disability
. Reduced life span extending into adulthood

Correct Answer & Explanation

. Hypotonia and delayed motor milestones

Explanation

Correct Answer: Hypotonia and delayed motor milestonesIn infancy, patients with achondroplasia typically present with hypotonia, and the acquisition of developmental motor milestones is often delayed. Intelligence and overall life span are usually normal.

Question 5680

Topic: 4. Pediatrics

While life span in achondroplasia is usually normal, there is an increased risk of death in infancy. Which of the following is a primary cause for this increased mortality risk?

. Severe congenital heart defects
. Upper airway obstruction and spinal cord compression
. Renal failure due to polycystic kidneys
. Recurrent severe pulmonary infections due to immunodeficiency
. Malignant hyperthermia

Correct Answer & Explanation

. Upper airway obstruction and spinal cord compression

Explanation

Correct Answer: Upper airway obstruction and spinal cord compressionCompression of the spinal cord (often at the foramen magnum) and upper airway obstruction are critical complications in infants with achondroplasia that significantly increase the risk of death during infancy.

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