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4. Pediatrics MCQs

Practice Set 307 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 6121

Topic: 4. Pediatrics

A 6-year-old child presents with a waddling gait, short stature, and joint pain. Radiographs demonstrate delayed, irregular ossification of multiple epiphyses and a 'double-layer' patella. A mutation in which of the following genes is most strongly associated with this phenotype?

. FGFR3
. COMP
. COL1A1
. RUNX2
. SLC26A2

Correct Answer & Explanation

. COMP

Explanation

Multiple Epiphyseal Dysplasia (MED) is frequently associated with mutations in the COMP (Cartilage Oligomeric Matrix Protein) gene. The 'double-layer' patella is a classic radiographic sign associated with this dysplasia.

Question 6122

Topic: 4. Pediatrics

A 3-month-old infant is evaluated for short limbs, a normal-sized trunk, frontal bossing, and midface hypoplasia. What is the primary pathophysiologic mechanism resulting from the mutated gene responsible for this condition?

. Decreased type 1 collagen synthesis
. Gain-of-function mutation causing premature inhibition of chondrocyte proliferation
. Defective sulfation of proteoglycans in cartilage matrix
. Impaired osteoclast function and bone resorption
. Failure of intramembranous ossification

Correct Answer & Explanation

. Gain-of-function mutation causing premature inhibition of chondrocyte proliferation

Explanation

Achondroplasia is caused by a gain-of-function mutation in FGFR3, which prematurely inhibits chondrocyte proliferation in the proliferative zone of the physis. This results in the characteristic rhizomelic dwarfism.

Question 6123

Topic: 4. Pediatrics

A newborn is noted to have severe micromelic dwarfism, 'hitchhiker' thumbs, clubfeet, and cystic swelling of the external ears (cauliflower ears). Which of the following inheritance patterns and gene mutations corresponds to this clinical picture?

. Autosomal dominant, COL1A1
. Autosomal recessive, SLC26A2 (DTDST)
. Autosomal dominant, COMP
. X-linked recessive, DMD
. Autosomal dominant, FGFR3

Correct Answer & Explanation

. Autosomal recessive, SLC26A2 (DTDST)

Explanation

Diastrophic dysplasia is characterized by hitchhiker thumbs, cauliflower ears, and severe clubfeet. It is an autosomal recessive disorder caused by mutations in the SLC26A2 gene, resulting in defective sulfate transport in cartilage.

Question 6124

Topic: 4. Pediatrics

A 6-year-old boy presents with short stature, a waddling gait, and bilateral knee pain. Radiographs reveal delayed ossification and fragmentation of multiple epiphyses, but the spine demonstrates normal vertebral body height and morphology. A mutation in which of the following genes is most likely responsible?

. COMP
. FGFR3
. COL1A1
. COL2A1
. RUNX2

Correct Answer & Explanation

. COMP

Explanation

The clinical picture describes Multiple Epiphyseal Dysplasia (MED), which typically spares the spine, distinguishing it from Spondyloepiphyseal Dysplasia (SED). MED is most commonly associated with mutations in the COMP (Cartilage Oligomeric Matrix Protein) gene.

Question 6125

Topic: 4. Pediatrics
A 3-year-old boy with blue sclerae and a history of multiple low-energy fractures is diagnosed with osteogenesis imperfecta (OI) type I. The pathogenesis of this condition is primarily related to a defect involving which of the following?
. Quantitative deficiency of structurally normal type I collagen
. Qualitative structural defect of type II collagen
. Quantitative deficiency of type IX collagen
. Mutation in cartilage oligomeric matrix protein (COMP)
. Activating mutation of fibroblast growth factor receptor 3

Correct Answer & Explanation

. Quantitative deficiency of structurally normal type I collagen

Explanation

OI type I is the mildest and most common form, caused by a quantitative defect (decreased production) of otherwise structurally normal type I collagen. OI types II, III, and IV generally involve qualitative structural defects.

Question 6126

Topic: 4. Pediatrics

A 4-year-old boy presents with disproportionate short stature, rhizomelic shortening, and frontal bossing. Which of the following genetic mutations is responsible for his condition?

. GNAS1 mutation
. COL1A1 mutation
. FGFR3 mutation
. RUNX2 mutation
. COMP mutation

Correct Answer & Explanation

. FGFR3 mutation

Explanation

Achondroplasia is caused by an activating mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. This mutation leads to an abnormal inhibition of chondrocyte proliferation in the proliferative zone of the physis.

Question 6127

Topic: 4. Pediatrics

A 3-year-old boy presents with his third fracture of the year, blue sclerae, and early hearing loss. A defect in which of the following is most likely responsible for his condition?

. Type II collagen
. Fibroblast growth factor receptor 3
. Type I collagen
. Fibrillin-1
. Core binding factor alpha 1

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is most commonly caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, causing defects in Type I collagen. This results in bone fragility, blue sclerae, and dentinogenesis imperfecta.

Question 6128

Topic: Pediatric Hip
A 6-year-old boy presents with a painless limp of 3 months duration. He has limited internal rotation and abduction of the right hip. Radiographs show sclerosis and fragmentation of the right capital femoral epiphysis. What is the primary etiology of this condition?
. Septic thrombosis of the femoral vein
. Idiopathic avascular necrosis of the capital femoral epiphysis
. Traumatic disruption of the ligamentum teres
. Slipped capital femoral epiphysis
. Hypercoagulable state leading to metaphyseal infarcts

Correct Answer & Explanation

. Idiopathic avascular necrosis of the capital femoral epiphysis

Explanation

Legg-Calvé-Perthes disease is an idiopathic avascular necrosis of the proximal femoral epiphysis in children. It typically presents between ages 4 and 8 with a painless limp and restricted hip motion, particularly in internal rotation and abduction.

Question 6129

Topic: 4. Pediatrics

A 2-month-old female infant is evaluated in the clinic. The examiner places the infant supine, flexes the hips to 90 degrees, and gently abducts the hips while applying anterior pressure to the greater trochanters. A palpable 'clunk' is felt as the femoral head reduces into the acetabulum. What is the name of this clinical test?

. Barlow maneuver
. Ortolani maneuver
. Galeazzi test
. Trendelenburg test
. Thomas test

Correct Answer & Explanation

. Ortolani maneuver

Explanation

Correct Answer: Ortolani maneuverThe Ortolani maneuver is a clinical test used to screen for Developmental Dysplasia of the Hip (DDH). It reduces a dislocated hip back into the acetabulum, producing a palpable 'clunk'. The Barlow maneuver, conversely, attempts to dislocate a reducible hip.

Question 6130

Topic: 4. Pediatrics

A 4-year-old boy presents with short stature, frontal bossing, and rhizomelic shortening of the limbs. Radiographs reveal narrowing of the interpedicular distances in the lumbar spine. Which of the following genetic mutations is most likely responsible for this condition?

. COL1A1
. FGFR3
. COMP
. RUNX2
. EXT1

Correct Answer & Explanation

. FGFR3

Explanation

Correct Answer: FGFR3The clinical and radiographic presentation is classic for achondroplasia, the most common form of short-limb dwarfism. It is caused by an activating mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene, which inhibits chondrocyte proliferation in the proliferative zone of the physis. COL1A1 mutations cause Osteogenesis Imperfecta. COMP mutations are associated with Multiple Epiphyseal Dysplasia and Pseudoachondroplasia. RUNX2 mutations cause Cleidocranial Dysplasia, and EXT1 mutations are seen in Multiple Hereditary Exostoses.

Question 6131

Topic: Pediatric Hip

An obese 13-year-old boy presents with a limp and vague knee pain. Examination reveals obligatory external rotation of the hip during passive flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). In which direction does the femoral neck typically displace relative to the capital epiphysis in this condition?

. Posterior and medial
. Anterior and lateral
. Posterior and lateral
. Anterior and medial
. Directly superior

Correct Answer & Explanation

. Anterior and lateral

Explanation

Correct Answer: Anterior and lateralIn a slipped capital femoral epiphysis (SCFE), the capital femoral epiphysis remains seated in the acetabulum while the femoral neck (metaphysis) displaces anteriorly and laterally. Although it is often conceptually described as the epiphysis slipping posteriorly and medially, the actual mechanical displacement involves the metaphysis moving anteriorly and laterally relative to the fixed epiphysis.

Question 6132

Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvé-Perthes disease. According to the Herring Lateral Pillar classification, which radiographic finding places the patient in Group C, indicating a poorer prognosis?
. No involvement of the lateral pillar
. >50% maintenance of lateral pillar height
. <50% maintenance of lateral pillar height
. Subchondral fracture line extending to the lateral pillar
. Metaphyseal cysts

Correct Answer & Explanation

. <50% maintenance of lateral pillar height

Explanation

The Herring Lateral Pillar classification is a key prognostic indicator in Legg-Calvé-Perthes disease, assessed during the fragmentation stage. Group A has no lateral pillar involvement. Group B maintains >50% of lateral pillar height. Group C maintains <50% of lateral pillar height and is associated with a poorer outcome, often requiring surgical containment (e.g., femoral or pelvic osteotomy) in children over 8 years of age.

Question 6133

Topic: Pediatric Hip

A 6-week-old female infant undergoes a screening ultrasound for Developmental Dysplasia of the Hip (DDH) due to a breech presentation. The ultrasound report notes a Graf Type IIa hip. What does this classification indicate, and what is the standard management?

. Normal mature hip; no follow-up needed
. Physiologically immature hip; follow-up ultrasound in 4-6 weeks
. Subluxated hip; immediate Pavlik harness application
. Dislocated hip; closed reduction and spica casting
. Teratologic dislocation; open reduction required

Correct Answer & Explanation

. Physiologically immature hip; follow-up ultrasound in 4-6 weeks

Explanation

Correct Answer: Physiologically immature hip; follow-up ultrasound in 4-6 weeksIn the Graf classification for DDH ultrasound, a Type I hip is normal (alpha angle >60 degrees). Type IIa indicates a physiologically immature hip in an infant less than 3 months old (alpha angle 50-59 degrees). The standard management is observation and a follow-up ultrasound in 4-6 weeks, as the vast majority will mature normally without intervention. Type IIb is the same angle but in an infant >3 months, which requires treatment.

Question 6134

Topic: 4. Pediatrics

A 4-year-old boy presents with short stature, frontal bossing, and rhizomelic shortening of the limbs. Radiographs show narrowing of the interpedicular distances in the lumbar spine. Which of the following is the most likely genetic mechanism responsible for this condition?

. Defect in type I collagen synthesis
. Mutation in the COMP gene
. Gain-of-function mutation in the FGFR3 gene
. Defect in the CBFA1 (RUNX2) transcription factor
. Mutation in the diastrophic dysplasia sulfate transporter (DTDST) gene

Correct Answer & Explanation

. Gain-of-function mutation in the FGFR3 gene

Explanation

Correct Answer: CAchondroplasia (Index 1.2.1) is the most common form of short-limb dwarfism. It is caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene, which abnormally inhibits chondrocyte proliferation in the proliferative zone of the physis. A defect in type I collagen is seen in Osteogenesis Imperfecta. COMP mutations are associated with Multiple Epiphyseal Dysplasia and Pseudoachondroplasia. CBFA1 mutations cause Cleidocranial Dysplasia.

Question 6135

Topic: Pediatric Hip
A 13-year-old obese boy presents with a 3-week history of left groin pain and a limp. On physical examination, as the left hip is passively flexed, it obligatorily deviates into external rotation. Radiographs show that a line drawn along the superior border of the femoral neck does not intersect the lateral portion of the femoral epiphysis. What is the most likely diagnosis?
. Legg-Calvé-Perthes disease
. Slipped Capital Femoral Epiphysis (SCFE)
. Developmental Dysplasia of the Hip (DDH)
. Transient synovitis
. Femoroacetabular Impingement (FAI)

Correct Answer & Explanation

. Slipped Capital Femoral Epiphysis (SCFE)

Explanation

The clinical presentation of an obese adolescent with groin pain, obligatory external rotation during hip flexion (Drehmann sign), and a radiograph showing failure of Klein's line to intersect the epiphysis is pathognomonic for Slipped Capital Femoral Epiphysis (SCFE).

Question 6136

Topic: Pediatric Hip
In the evaluation of a 7-year-old boy with Legg-Calvé-Perthes disease, the treating orthopedic surgeon utilizes the Herring lateral pillar classification to determine prognosis. During which stage of the disease is this classification system most accurately applied?
. Initial (necrosis) stage
. Early fragmentation stage
. Late fragmentation stage
. Reossification stage
. Residual stage

Correct Answer & Explanation

. Early fragmentation stage

Explanation

The Herring lateral pillar classification is used to predict the outcome in Legg-Calvé-Perthes disease. It is based on the height of the lateral pillar of the capital femoral epiphysis on an AP radiograph. It is most accurately applied during the early fragmentation stage of the disease. Applying it too early (in the initial stage) may underestimate the extent of lateral pillar involvement and lead to an inaccurate prognosis.

Question 6137

Topic: 4. Pediatrics

A 6-year-old girl is evaluated for a short neck, low posterior hairline, and severely restricted cervical range of motion. Radiographs confirm congenital fusion of multiple cervical vertebrae. Which of the following organ systems must be routinely evaluated due to a high association with this syndrome?

. Gastrointestinal system
. Genitourinary system
. Endocrine system
. Hematopoietic system
. Pulmonary system

Correct Answer & Explanation

. Genitourinary system

Explanation

Correct Answer: BThe patient has Klippel-Feil Syndrome (Index 14.1.1), characterized by the classic triad of a short neck, low posterior hairline, and limited neck motion due to congenital fusion of cervical vertebrae. Up to 30-50% of these patients have associated genitourinary anomalies (e.g., unilateral renal agenesis, horseshoe kidney), making routine renal ultrasound a mandatory part of their initial evaluation.

Question 6138

Topic: 4. Pediatrics

A 4-year-old boy presents with short stature, rhizomelic shortening of the limbs, frontal bossing, and a trident hand. Radiographs show narrowing of the interpedicular distances in the lumbar spine. Which of the following is the most likely genetic mutation responsible for this condition?

. COL1A1
. FGFR3
. COMP
. RUNX2
. EXT1

Correct Answer & Explanation

. FGFR3

Explanation

Correct Answer: B (FGFR3)The clinical picture describes Achondroplasia, the most common form of short-limb dwarfism. It is an autosomal dominant condition caused by an activating mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene, which inhibits chondrocyte proliferation in the proliferative zone of the physis. COL1A1 is associated with Osteogenesis Imperfecta, COMP with Multiple Epiphyseal Dysplasia, RUNX2 with Cleidocranial Dysplasia, and EXT1 with Multiple Hereditary Exostoses.

Question 6139

Topic: Pediatric Hip

In a patient with a Slipped Capital Femoral Epiphysis (SCFE), the proximal femoral epiphysis typically displaces in which direction relative to the femoral neck?

. Anterior and superior
. Anterior and inferior
. Posterior and inferior
. Posterior and superior
. Directly medial

Correct Answer & Explanation

. Posterior and inferior

Explanation

Correct Answer: C (Posterior and inferior)In SCFE, the femoral neck displaces anteriorly and superiorly relative to the epiphysis. Therefore, the epiphysis is displaced posteriorly and inferiorly relative to the femoral neck. This biomechanical relationship dictates the typical external rotation deformity and obligate external rotation with hip flexion seen clinically.

Question 6140

Topic: 4. Pediatrics

A 6-year-old girl is diagnosed with Klippel-Feil syndrome based on a short neck, low posterior hairline, and limited cervical range of motion. Radiographs confirm congenital fusion of multiple cervical vertebrae. Which of the following organ systems must be routinely evaluated due to a high rate of associated congenital anomalies?

. Gastrointestinal
. Genitourinary
. Endocrine
. Hematopoietic
. Pulmonary

Correct Answer & Explanation

. Genitourinary

Explanation

Correct Answer: B (Genitourinary)Klippel-Feil syndrome is characterized by congenital fusion of two or more cervical vertebrae. It is highly associated with other congenital anomalies, most notably genitourinary tract anomalies (up to 30-40%, such as unilateral renal agenesis), cardiovascular anomalies, and Sprengel's deformity. A renal ultrasound is mandatory in these patients.

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