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4. Pediatrics MCQs

Practice Set 39 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 761

Topic: 4. Pediatrics

A 4-year-old child presents with short-limb dwarfism and a waddling gait. Unlike typical achondroplasia, this child has a completely normal facial appearance and head circumference. Radiographs show small, irregular epiphyses and metaphyseal flaring. What gene is mutated?

. COMP
. FGFR3
. COL2A1
. SOX9
. FBN1

Correct Answer & Explanation

. COMP

Explanation

Pseudoachondroplasia is caused by mutations in the COMP gene. Unlike achondroplasia, patients with pseudoachondroplasia have a normal facies and normal intelligence, along with severe epiphyseal and metaphyseal dysplasia.

Question 762

Topic: 4. Pediatrics

A 3-year-old child presents with coarse facial features, severe mental retardation, corneal clouding, and hepatosplenomegaly. Radiographs reveal thick, spatula-like ribs and hypoplastic vertebral bodies with inferior beaking. Which enzyme is deficient?

. Iduronate-2-sulfatase
. Alpha-L-iduronidase
. Galactosamine-6-sulfatase
. Beta-galactosidase
. Glucocerebrosidase

Correct Answer & Explanation

. Alpha-L-iduronidase

Explanation

Hurler syndrome (MPS I) is caused by a deficiency in alpha-L-iduronidase. Radiographically, it demonstrates dysostosis multiplex, including inferior vertebral beaking, contrasting with Morquio syndrome's central beaking.

Question 763

Topic: 4. Pediatrics

A 1-year-old infant with achondroplasia exhibits a 40-degree thoracolumbar kyphosis when sitting. Neurological examination is normal. What is the most appropriate initial management for this spinal deformity?

. Immediate posterior spinal fusion
. Anterior and posterior spinal fusion
. Avoidance of unsupported sitting
. Thoracolumbosacral orthosis (TLSO) bracing for 23 hours a day
. Observation with no restrictions

Correct Answer & Explanation

. Avoidance of unsupported sitting

Explanation

Thoracolumbar kyphosis in infantile achondroplasia is common and largely resolves when the child begins walking and develops lumbar lordosis. The primary initial management is to avoid unsupported sitting to prevent progression into a fixed structural deformity.

Question 764

Topic: 4. Pediatrics

A 6-year-old boy presents with disproportionate short-limb dwarfism and a waddling gait. His facial features are entirely normal. Radiographs reveal delayed, fragmented epiphyseal ossification and anterior tongue-like projections of the vertebral bodies. Which of the following genes or proteins is most likely mutated in this patient?

. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)
. Type II collagen (COL2A1)
. Runt-related transcription factor 2 (RUNX2)
. Core-binding factor subunit alpha-1 (CBFA1)

Correct Answer & Explanation

. Cartilage oligomeric matrix protein (COMP)

Explanation

The clinical presentation is characteristic of pseudoachondroplasia, which features short-limb dwarfism but normal facies, differentiating it from achondroplasia. It is caused by mutations in the COMP gene, leading to accumulation of mutant protein in the rough endoplasmic reticulum of chondrocytes.

Question 765

Topic: Pediatric Hip

A 4-year-old child presents with a widened cranial vault, frontal bossing, and delayed closure of the fontanelles. On examination, he is able to bring his shoulders together anteriorly without discomfort. Which of the following orthopedic conditions is most frequently associated with this syndrome?

. Developmental dysplasia of the hip
. Coxa vara
. Anterolateral bowing of the tibia
. Posteromedial bowing of the tibia
. Slipped capital femoral epiphysis

Correct Answer & Explanation

. Coxa vara

Explanation

This patient has cleidocranial dysplasia, an autosomal dominant condition caused by a RUNX2 (CBFA1) mutation resulting in clavicular hypoplasia. Coxa vara is the most common and significant orthopedic manifestation, occurring in up to one-third of these patients.

Question 766

Topic: Pediatric Hip

A 4-year-old boy with disproportionate short-trunk dwarfism is evaluated in the clinic. He has a history of a cleft palate and severe myopia. Radiographs reveal delayed ossification of the pubic bones, severe coxa vara, and platyspondyly. This condition is caused by a mutation affecting which of the following?

. Type I collagen
. Type II collagen
. Type IX collagen
. Type X collagen
. Fibroblast growth factor receptor 3

Correct Answer & Explanation

. Type II collagen

Explanation

Spondyloepiphyseal dysplasia congenita (SEDC) is characterized by short-trunk dwarfism, coxa vara, cleft palate, and visual impairments like myopia or retinal detachment. It is an autosomal dominant disorder caused by a mutation in the COL2A1 gene, affecting Type II collagen.

Question 767

Topic: 4. Pediatrics

A newborn infant presents with asymmetric limb shortening, bilateral cataracts, and ichthyosis. Radiographs reveal multiple stippled, punctate calcifications in the unossified epiphyses of the long bones. This clinical and radiographic presentation is most characteristic of:

. Osteopathia striata
. Melorheostosis
. Chondrodysplasia punctata
. Diastrophic dysplasia
. Metaphyseal chondrodysplasia

Correct Answer & Explanation

. Chondrodysplasia punctata

Explanation

Chondrodysplasia punctata (such as the Conradi-Hunermann X-linked dominant type) is characterized by "stippled epiphyses" on radiographs in infancy. Associated clinical findings typically include asymmetric limb shortening, cataracts, and skin changes like ichthyosis.

Question 768

Topic: 4. Pediatrics

A 5-year-old boy presents with disproportionate short stature, a waddling gait, and joint laxity. His facial features are entirely normal, and his intelligence is intact. Radiographs reveal delayed epiphyseal ossification and metaphyseal irregularities. What is the most likely genetic mutation responsible for this condition?

. FGFR3
. COL1A1
. COMP
. CBFA1
. COL2A1

Correct Answer & Explanation

. COMP

Explanation

Pseudoachondroplasia is an autosomal dominant skeletal dysplasia caused by a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene. Unlike achondroplasia, patients have a normal craniofacial appearance and normal intelligence.

Question 769

Topic: 4. Pediatrics

A 6-year-old child with a known skeletal dysplasia presents with neck pain and mild myelopathic symptoms. He is noted to have a short trunk, barrel chest, and severe myopia. Hand and foot radiographs show normal bone length and morphology. Which of the following is the most likely diagnosis?

. Diastrophic dysplasia
. Achondroplasia
. Spondyloepiphyseal dysplasia congenita
. Pseudoachondroplasia
. Multiple epiphyseal dysplasia

Correct Answer & Explanation

. Spondyloepiphyseal dysplasia congenita

Explanation

Spondyloepiphyseal dysplasia congenita is a type II collagen disorder (COL2A1) characterized by short-trunk dwarfism, normal hands and feet, and a high risk of myopia and retinal detachment. Cervical spine instability (atlantoaxial) is a critical complication requiring careful monitoring.

Question 770

Topic: 4. Pediatrics

In a newborn diagnosed with achondroplasia, what is the most common cause of mortality during the first year of life?

. Respiratory distress from severe restrictive lung disease
. Cardiac arrhythmias
. Compression of the cervicomedullary junction
. Hydrocephalus
. Intussusception

Correct Answer & Explanation

. Compression of the cervicomedullary junction

Explanation

The most common cause of mortality in infants with achondroplasia is sudden death due to central apnea, resulting from cervicomedullary compression at a stenotic foramen magnum. Early screening with MRI or CT of the craniocervical junction is essential.

Question 771

Topic: 4. Pediatrics

A neonate presents with multiple fractures, blue sclerae, and profound osteopenia on radiographs. Genetic testing confirms Osteogenesis Imperfecta (OI) type II. Which of the following mutations is typically responsible for this specific, lethal form of OI?

. Null mutation resulting in a quantitative decrease in type I collagen
. Missense mutation resulting in a qualitative defect of type I collagen
. FGFR3 point mutation
. COMP gene mutation
. CBFA1 gene mutation

Correct Answer & Explanation

. Missense mutation resulting in a qualitative defect of type I collagen

Explanation

Osteogenesis Imperfecta Type II is typically caused by a qualitative defect (often a missense mutation causing a glycine substitution) in the COL1A1 or COL1A2 genes, resulting in structurally abnormal collagen and early perinatal lethality. In contrast, the milder Type I OI typically results from a quantitative decrease (null mutation).

Question 772

Topic: 4. Pediatrics

A 7-year-old boy with diplegic cerebral palsy has had lengthening of his hamstrings and heelcords. He is examined 2 years later. He walks with the knees nearly straight throughout the gait cycle and circumducts each extremity during swing. This pattern is most likely due to:

. Recurrent hamstring tightness
. Overlengthening of the heelcords
. Spasticity of the rectus femoris
. Contracture of the tensor fascia lata
. Spasticity of the psoas muscle

Correct Answer & Explanation

. Spasticity of the rectus femoris

Explanation

The straight legs and circumduction suggest spasticity of the rectus femoris as the most likely cause. Recurrent hamstring tightness (by itself) would cause the opposite combination of problems. Overlengthening of the heelcords usually causes increased dorsiflexion at the ankles and would help to increase the flexion moment rather than the extension. Contracture of the tensor fascia lata is extremely rare in cerebral palsy. Spasticity in the psoas muscle would not lead to a stiff knee gait.

Question 773

Topic: 4. Pediatrics

A 6-year-old girl with osteogenesis imperfecta has severe bowing of both femurs. The family is interested in surgery to correct the condition. This method will give her the longest interval between procedures in the future:

. Closed osteoclasis and cast application
. Multiple osteotomies and realignment over a single smooth rod
. Multiple osteotomies and realignment over parallel rods
. Multiple osteotomies and realignment over telescoping rods
. Excision of the abnormal bone and replacement with allograft

Correct Answer & Explanation

. Multiple osteotomies and realignment over telescoping rods

Explanation

Telescoping or Bailey-Dubow rods are able to grow with the patient and maintain stabilization for a mean of 4 years between operations in growing children. Without the addition of internal fixation, bowing is likely to resume. Although a single rod is likely to provide current stability, bowing is likely to occur as the patient grows and the bone becomes longer than the rod. Parallel rods do not interlock and are likely to splay and lose fixation. There are no reports of large segment allograft replacement for diaphyses in osteogenesis imperfecta. In the absence of internal fixation, bowing is likely to resume as growth occurs.

Question 774

Topic: 4. Pediatrics

An infant is seen in the office for the first time. She has slender, stiff fingers with few creases, elbow range of motion 20° to 45°, and internally rotated arms. Her legs are flexed and externally rotated at the hip. Knee range of motion is 15° to 40° of flexion, and she has bilateral clubfeet that are stiff. The most likely diagnosis is:

. Larsen syndrome
. C erebral palsy
. Ehlers-Danlos syndrome
. Down syndrome
. Arthrogryposis

Correct Answer & Explanation

. Arthrogryposis

Explanation

The patient has enough joint contractures to make arthrogryposis a likely diagnosis. Larsen syndrome is characterized by dislocation of multiple joints. Cerebral palsy is characterized by spasticity and flexors overpowering extensors. Ehlers-Danlos is characterized by hyperlaxity of the large joints. Down syndrome does not present with stiffness.

Question 775

Topic: Pediatric Lower Extremity

Which of the following statements best characterizes the natural history of metatarsus adductus in a newborn:

. Metatarsus adductus is likely to become fixed if not treated with casts.
. Metatarsus adductus is likely to become fixed if not treated by 6 months.
. Metatarsus adductus is likely to become fixed if not surgically corrected.
. Metatarsus adductus is likely to later develop hindfoot equinus.
. Most infants will improve spontaneously.

Correct Answer & Explanation

. Most infants will improve spontaneously.

Explanation

Virtually all patients with metatarsus adductus will improve with time in the absence of active treatment. Casts are not needed for the majority of cases because spontaneous improvement is by far the most common outcome. Reverse last shoes are not needed in the majority of patients with metatarsus adductus. Most patients will not need surgery. Equinus of the hindfoot is not part of the pathology in metatarsus adductus.

Question 776

Topic: 4. Pediatrics

A 6-year-old child suffers a displaced fracture of the distal humerus in the supracondylar region. Neurologic and vascular exams are normal. The surgeon decides to reduce and pin the fracture. Which of the following risks increases if the procedure is delayed more than 8 hours?

. Brachial artery damage
. Median nerve palsy
. Radial nerve palsy
. Need for an open reduction
. No risks increase

Correct Answer & Explanation

. No risks increase

Explanation

A retrospective comparison study has shown no increase of risks in delayed treatment of supracondylar fractures.

Question 777

Topic: Pediatric Hip

A 14-year-old obese boy presents with acute-on-chronic slipped capital femoral epiphysis (SCFE). He undergoes in situ pinning. What is the most significant risk factor for developing chondrolysis in this patient?

. Unrecognized pin penetration into the joint
. Severity of the slip
. Acute nature of the presentation
. Patient obesity
. Delayed surgical intervention

Correct Answer & Explanation

. Unrecognized pin penetration into the joint

Explanation

Unrecognized hardware penetration into the joint is the most consistently identified risk factor for chondrolysis following the surgical treatment of SCFE. Accurate intraoperative fluoroscopy is critical to confirm the pin is completely within the femoral head.

Question 778

Topic: Pediatric Hip

A 6-month-old infant is diagnosed with DDH that failed Pavlik harness treatment. A closed reduction and spica casting are planned. Under fluoroscopy, the "safe zone" of Ramsey is evaluated. What does this zone represent?

. The arc between maximal abduction and the angle of re-dislocation
. The arc between 90 degrees of flexion and maximal extension
. The arc between maximal internal and external rotation
. The arc between the angle of subluxation and 30 degrees of adduction
. The arc between 30 and 60 degrees of hip flexion

Correct Answer & Explanation

. The arc between maximal abduction and the angle of re-dislocation

Explanation

The "safe zone" of Ramsey is the arc of hip abduction between the angle of maximal abduction (limited by adductor tightness) and the lower angle at which the hip redislocates or subluxates as it is adducted. If the safe zone is too narrow, an adductor tenotomy may be required.

Question 779

Topic: 4. Pediatrics
A 7-year-old boy presents with a painless limp. Hip radiographs reveal a fragmented, flattened capital femoral epiphysis consistent with Legg-Calvé-Perthes disease. Which of the following is considered one of Catterall's "head-at-risk" signs?
. Medial subluxation of the femoral head
. Gage sign
. Increased neck-shaft angle (coxa valga)
. Premature central physeal closure
. Ossification of the acetabular limbus

Correct Answer & Explanation

. Gage sign

Explanation

In Legg-Calvé-Perthes disease, Catterall's "head-at-risk" signs portend a poorer prognosis. They include Gage sign (a V-shaped radiolucency in the lateral epiphysis and adjacent metaphysis), lateral (not medial) subluxation, calcification lateral to the epiphysis, and a horizontal physis.

Question 780

Topic: Pediatric Hip

A 7-month-old girl presents with a persistently dislocated left hip after 6 weeks of compliant Pavlik harness treatment. What is the most appropriate next step in management?

. Continue the Pavlik harness for 6 additional weeks
. Examination under anesthesia, closed reduction, and spica casting
. Immediate femoral varus derotational osteotomy
. Salter innominate osteotomy
. Switch to a rigid abduction orthosis for 12 weeks

Correct Answer & Explanation

. Examination under anesthesia, closed reduction, and spica casting

Explanation

In an infant older than 6 months or after failed Pavlik harness treatment, the next appropriate step is an examination under anesthesia and an attempted closed reduction with spica casting. Continued use of the Pavlik harness after failure increases the risk of "Pavlik harness disease" and structural damage.

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