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4. Pediatrics MCQs

Practice Set 187 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 3721

Topic: 4. Pediatrics

A 14-year-old elite adolescent baseball pitcher presents with generalized, progressive right shoulder pain during throwing over the past two months. He denies any acute traumatic event. Examination reveals tenderness over the lateral aspect of the proximal humerus but normal range of motion. Radiographs demonstrate widening, sclerosis, and irregularity of the proximal humeral physis. What is the most appropriate initial management?

. Immediate shoulder spica casting for 6 weeks
. Absolute rest from throwing for 3 months followed by a progressive interval throwing program
. MRI arthrogram to evaluate for a concomitant superior labral tear
. Corticosteroid injection into the subacromial space
. Arthroscopic evaluation and physeal pinning

Correct Answer & Explanation

. Absolute rest from throwing for 3 months followed by a progressive interval throwing program

Explanation

This presentation describes 'Little League Shoulder' (epiphysiolysis of the proximal humerus), an overuse injury in skeletally immature throwers. The mainstay of treatment is absolute rest from throwing (usually up to 3 months) to allow physeal healing, followed by a structured return-to-throwing program.

Question 3722

Topic: 4. Pediatrics

A 14-year-old boy with multiple palpable bone masses presents for evaluation. Radiographs reveal multiple pedunculated and sessile osteochondromas. A mutation in the EXT1 gene is suspected. This gene mutation primarily affects which of the following processes?

. Collagen cross-linking
. Heparan sulfate synthesis
. Fibroblast growth factor receptor 3 (FGFR3) inhibition
. Carbonic anhydrase II production
. Wnt signaling regulation

Correct Answer & Explanation

. Heparan sulfate synthesis

Explanation

Multiple hereditary exostoses is caused by mutations in the EXT1 or EXT2 genes. These genes encode glycosyltransferases essential for the synthesis of heparan sulfate, leading to abnormal chondrocyte proliferation.

Question 3723

Topic: 4. Pediatrics

A 5-year-old boy presents with multiple fractures, blue sclerae, and hearing loss. This condition is most commonly caused by a mutation affecting which of the following proteins?

. Fibrillin-1
. Type II collagen
. Type I collagen
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Type I collagen

Explanation

The clinical presentation is classic for Osteogenesis Imperfecta (OI). OI is predominantly caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which lead to qualitative or quantitative defects in Type I collagen.

Question 3724

Topic: 4. Pediatrics

A 4-year-old child presents with a history of multiple low-energy long bone fractures, blue sclerae, and dentinogenesis imperfecta. This clinical syndrome is most commonly caused by an autosomal dominant mutation affecting which of the following?

. Type II collagen
. Type I collagen
. Fibroblast growth factor receptor 3 (FGFR3)
. Core binding factor alpha 1 (CBFA1 / RUNX2)
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is primarily a disorder of Type I collagen synthesis or processing, most frequently caused by mutations in the COL1A1 or COL1A2 genes. This defect leads to brittle bones and distinctive extraskeletal manifestations.

Question 3725

Topic: 4. Pediatrics

Acollegial review of a pediatric patient with rhizomelic short stature and frontal bossing is conducted. Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene. This mutation primarily causes the phenotype by which mechanism?

. Excessive proliferation of chondrocytes in the reserve zone
. Constitutive inhibition of chondrocyte proliferation in the proliferative zone
. Failure of osteoid mineralization in the hypertrophic zone
. Premature apoptosis of osteoblasts in the primary spongiosa
. Defective synthesis of Type II collagen

Correct Answer & Explanation

. Constitutive inhibition of chondrocyte proliferation in the proliferative zone

Explanation

The gain-of-function mutation in the FGFR3 gene causes constitutive activation of the receptor. This inappropriately inhibits chondrocyte proliferation in the proliferative zone of the physis, dramatically slowing down endochondral ossification.

Question 3726

Topic: 4. Pediatrics
A 6-year-old child presents with joint pain, perifollicular hemorrhages, and radiographic evidence of a radiolucent band adjacent to the physis (Trümmerfeld zone). The underlying biochemical defect involves the impaired function of which of the following enzymes?
. Lysyl oxidase
. Prolyl hydroxylase
. Farnesyl pyrophosphate synthase
. Alkaline phosphatase
. Cathepsin K

Correct Answer & Explanation

. Prolyl hydroxylase

Explanation

The presentation is consistent with scurvy (Vitamin C deficiency). Ascorbic acid is a required cofactor for prolyl hydroxylase and lysyl hydroxylase, which are essential for proper collagen cross-linking and stability.

Question 3727

Topic: 4. Pediatrics

During endochondral ossification, which zone of the physis is primarily affected in achondroplasia?

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

Correct Answer & Explanation

. Proliferative zone

Explanation

Achondroplasia is caused by an activating mutation in FGFR3, which inhibits chondrocyte proliferation. Thus, the proliferative zone of the physis is primarily affected, leading to shortened long bones.

Question 3728

Topic: 4. Pediatrics

A newborn is noted to have multiple fractures, blue sclerae, and hearing loss. This condition is primarily due to a genetic defect affecting which process?

. Carbonic anhydrase II function
. Degradation of glycosaminoglycans
. Synthesis of Type I collagen
. Mineralization of osteoid
. Fibroblast growth factor receptor 3 signaling

Correct Answer & Explanation

. Synthesis of Type I collagen

Explanation

Osteogenesis imperfecta is characterized by brittle bones, blue sclerae, and hearing loss. It is most commonly caused by mutations in the COL1A1 or COL1A2 genes, which impair the synthesis and structure of Type I collagen.

Question 3729

Topic: 4. Pediatrics

The skeletal manifestations of achondroplasia are primarily due to a gain-of-function mutation that leads to which of the following cellular events?

. Increased proliferation of chondrocytes in the reserve zone
. Decreased hypertrophy of chondrocytes in the proliferative zone
. Inhibition of chondrocyte proliferation in the growth plate
. Excessive production of type I collagen by osteoblasts
. Premature apoptosis of osteoclasts

Correct Answer & Explanation

. Inhibition of chondrocyte proliferation in the growth plate

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene. Overactivity of the FGFR3 receptor strongly inhibits chondrocyte proliferation and differentiation in the growth plate, severely impairing endochondral ossification.

Question 3730

Topic: Pediatric Upper Extremity & Spine

A patient presents with median nerve compression symptoms above the elbow. Imaging reveals a supracondylar process. The ligament of Struthers connects this process to which anatomical structure?

. Lateral epicondyle
. Medial epicondyle
. Olecranon
. Radial tuberosity
. Coronoid process

Correct Answer & Explanation

. Medial epicondyle

Explanation

The ligament of Struthers is a fibrous band that extends from an anomalous supracondylar process on the anteromedial humerus to the medial epicondyle. It can compress the median nerve and brachial artery.

Question 3731

Topic: 4. Pediatrics

In a growing child, most Salter-Harris fractures typically propagate through which specific histologic zone of the physis?

. Reserve zone
. Proliferative zone
. Zone of maturation
. Zone of provisional calcification
. Zone of hypertrophy

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Salter-Harris fractures typically propagate through the zone of hypertrophy. This zone is the structurally weakest portion of the physis because it lacks both type II collagen and a mineralized matrix.

Question 3732

Topic: Pediatric Upper Extremity & Spine

A patient presents with an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger after a supracondylar humerus fracture. The affected nerve normally passes between the two heads of which muscle?

. Flexor carpi ulnaris
. Pronator teres
. Supinator
. Flexor digitorum superficialis
. Brachioradialis

Correct Answer & Explanation

. Pronator teres

Explanation

The clinical presentation describes anterior interosseous nerve (AIN) palsy. The AIN is a branch of the median nerve, which enters the forearm by passing between the superficial and deep heads of the pronator teres.

Question 3733

Topic: Pediatric Upper Extremity & Spine

A baseball pitcher undergoes ulnar collateral ligament (UCL) reconstruction. The graft is secured anatomically to the sublime tubercle. On which specific anatomical structure is the sublime tubercle located?

. Anterior medial epicondyle
. Anteromedial aspect of the coronoid process
. Lateral aspect of the olecranon
. Radial tuberosity
. Medial supracondylar ridge

Correct Answer & Explanation

. Anteromedial aspect of the coronoid process

Explanation

The anterior bundle of the UCL is the primary restraint to valgus stress at the elbow. It originates on the anterior undersurface of the medial epicondyle and inserts on the sublime tubercle of the anteromedial coronoid process.

Question 3734

Topic: 4. Pediatrics

A 3-year-old child presents with disproportionate dwarfism and the oral anomaly shown in the clinical photograph below. Based on the most likely syndromic diagnosis, which of the following congenital cardiac defects is most classically associated with this condition?



. Atrial septal defect
. Patent ductus arteriosus
. Ventricular septal defect
. Tetralogy of Fallot
. Coarctation of the aorta

Correct Answer & Explanation

. Ventricular septal defect

Explanation

Correct Answer: Ventricular septal defectThe image demonstrates fusion of the upper lip to the gingival margin in a patient with disproportionate dwarfism, which is highly characteristic of Chondroectodermal Dysplasia (Ellis-van Creveld's syndrome). Congenital heart disease is a hallmark of this syndrome, most commonly presenting as a ventricular septal defect (VSD) or a common atrium.

Question 3735

Topic: 4. Pediatrics

Ellis-van Creveld syndrome is a generalized disorder of the maturation of enchondral ossification. The genetic mutation associated with this syndrome is linked to the HOX7 marker, which is located proximal to the gene responsible for the achondroplasia phenotype. Which of the following is that gene?

. COL1A1
. FGFR3
. COMP
. RUNX2
. SOX9

Correct Answer & Explanation

. FGFR3

Explanation

Correct Answer: FGFR3The link of the Ellis-van Creveld's syndrome gene to marker HOX7 is in a region proximal to the FGFR3 gene. Mutations in the FGFR3 (Fibroblast Growth Factor Receptor 3) gene are responsible for the achondroplasia phenotype. Both conditions present with dwarfism, but they have distinct genetic loci and inheritance patterns.

Question 3736

Topic: 4. Pediatrics

A patient presents with the foot deformities and corresponding radiographs shown below. If this patient is diagnosed with Ellis-van Creveld syndrome, what is the inheritance pattern of this condition?



. Autosomal dominant
. X-linked dominant
. Autosomal recessive
. X-linked recessive
. Mitochondrial

Correct Answer & Explanation

. Autosomal recessive

Explanation

Correct Answer: Autosomal recessiveThe images show shortening of the digits of the toes and feet with short tubular bones on the radiograph, consistent with Ellis-van Creveld's syndrome. This syndrome is inherited in an autosomal recessive manner, unlike achondroplasia which is autosomal dominant.

Question 3737

Topic: 4. Pediatrics

A neonate is evaluated for disproportionate short stature and short limbs. Oral examination reveals multiple frenula and notching of the lower alveolar process. Which of the following dental findings is also highly characteristic of this patient's suspected syndrome?

. Macrodontic teeth
. Delayed eruption of primary teeth
. Hyperdontia (supernumerary teeth)
. Enamel hypoplasia without missing teeth
. Neonatal teeth

Correct Answer & Explanation

. Neonatal teeth

Explanation

Correct Answer: Neonatal teethOral findings play an important role in the diagnosis of Ellis-van Creveld syndrome. These include fusion of the upper lip to the gingival margin, multiple frenula, abnormally shaped and microdontic (not macrodontic) teeth, congenital missing teeth, malocclusion, neonatal teeth, and notching of the lower alveolar process.

Question 3738

Topic: 4. Pediatrics

Ellis-van Creveld syndrome shares some phenotypic similarities with achondroplasia, such as disproportionate dwarfism. However, which of the following features is a hallmark of Ellis-van Creveld syndrome that helps distinguish it clinically from achondroplasia?

. Normal stature
. Frontal bossing
. Rhizomelic shortening only
. Postaxial polydactyly
. Autosomal dominant inheritance

Correct Answer & Explanation

. Postaxial polydactyly

Explanation

Correct Answer: Postaxial polydactylyPostaxial polydactyly is a classic feature of Ellis-van Creveld syndrome (Chondroectodermal Dysplasia) and is not a typical feature of achondroplasia. Furthermore, Ellis-van Creveld is autosomal recessive, whereas achondroplasia is autosomal dominant. Achondroplasia is more classically associated with frontal bossing and rhizomelic shortening.

Question 3739

Topic: 4. Pediatrics

The clinical photograph below shows a patient with disproportionate dwarfism and a characteristic oral anomaly. Which of the following oral or dental findings is also a hallmark of this syndrome?




. Mandibular prognathism
. Cleft palate
. Neonatal teeth
. Macroglossia
. Delayed eruption of permanent teeth

Correct Answer & Explanation

. Neonatal teeth

Explanation

Correct Answer: CThe image shows fusion of the upper lip to the gingival margin. Other variable but characteristic oral findings in Ellis-van Creveld syndrome include multiple frenula, abnormally shaped and microdontic teeth, congenital missing teeth, malocclusion, neonatal teeth, and notching of the lower alveolar process.

Question 3740

Topic: 4. Pediatrics

Genetic analysis of a patient with Ellis-van Creveld syndrome is likely to show a linkage to which of the following markers, located proximal to the FGFR3 gene?

. SOX9
. HOX7
. RUNX2
. COL2A1
. COMP

Correct Answer & Explanation

. HOX7

Explanation

Correct Answer: BThe link of the Ellis-van Creveld syndrome gene to marker HOX7 in a region proximal to the FGFR3 gene is responsible for the achondroplasia-like phenotype seen in these patients.

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