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4. Pediatrics MCQs

Practice Set 189 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 3761

Topic: 4. Pediatrics

Look at the image provided.

A 7-year-old boy with short stature and dystrophic nails presents with severe knock-knees. Radiographs show a characteristic defect. Which underlying mechanism best explains this patient's syndrome?

. Defect in FGFR3 signaling
. Mutation in COMP gene
. Mutation in Type I collagen
. Defect in diastrophic dysplasia sulfate transporter
. Defect in ciliary function (EVC and EVC2 genes)

Correct Answer & Explanation

. Defect in ciliary function (EVC and EVC2 genes)

Explanation

The patient has Ellis-van Creveld syndrome, characterized by lateral tibial plateau depression, short stature, and ectodermal defects. It is a ciliopathy caused by mutations in the EVC or EVC2 genes, which encode proteins localizing to the basal body of primary cilia.

Question 3762

Topic: 4. Pediatrics

Ellis-van Creveld syndrome is characterized by a specific pattern of limb shortening that differentiates it from other skeletal dysplasias. Which of the following describes the typical pattern seen in these patients?

. Purely rhizomelic
. Entirely proportionate
. Isolated rhizomelic shortening of the upper extremities
. Mesomelic and acromelic
. Hemihypertrophy

Correct Answer & Explanation

. Mesomelic and acromelic

Explanation

The short-limb dwarfism in Ellis-van Creveld syndrome is typically mesomelic (middle segment, i.e., forearms and lower legs) and acromelic (distal segment, i.e., hands and feet). This contrasts with achondroplasia, which is predominantly rhizomelic.

Question 3763

Topic: 4. Pediatrics

A 5-year-old with Ellis-van Creveld syndrome has progressive, symptomatic genu valgum due to lateral tibial plateau hypoplasia. Which of the following is the most appropriate initial surgical intervention?

. Total knee arthroplasty
. Lateral closing wedge tibial osteotomy
. Medial hemiepiphysiodesis (guided growth) of the proximal tibia
. Distal femoral varus producing osteotomy
. Complete physeal ablation

Correct Answer & Explanation

. Medial hemiepiphysiodesis (guided growth) of the proximal tibia

Explanation

For growing children with progressive genu valgum in Ellis-van Creveld syndrome, medial hemiepiphysiodesis (guided growth) of the proximal tibia is the preferred initial, minimally invasive surgical intervention. Osteotomies are reserved for severe, rigid deformities or near skeletal maturity.

Question 3764

Topic: 4. Pediatrics

The EVC and EVC2 genes associated with Ellis-van Creveld syndrome encode proteins that localize to the basal body of primary cilia. This ciliary dysfunction primarily disrupts which of the following cellular signaling pathways vital for chondrocyte proliferation?

. Wnt/beta-catenin pathway
. Notch signaling
. Indian Hedgehog (Ihh) pathway
. TGF-beta pathway
. FGF/FGFR3 pathway

Correct Answer & Explanation

. Indian Hedgehog (Ihh) pathway

Explanation

Primary cilia are essential for the proper transduction of the Indian Hedgehog (Ihh) signaling pathway. Disruption of EVC/EVC2 at the ciliary basal body impairs Ihh signaling, leading to defective chondrocyte proliferation in the growth plate.

Question 3765

Topic: 4. Pediatrics

A 6-year-old boy with Ellis-van Creveld syndrome presents for evaluation of a progressive lower extremity deformity. Which of the following is the most likely cause of his genu valgum?

. Overgrowth of the medial femoral condyle
. Hypoplasia of the lateral aspect of the proximal tibial epiphysis
. Premature closure of the medial distal femoral physis
. Laxity of the medial collateral ligament
. Fibular hemimelia

Correct Answer & Explanation

. Hypoplasia of the lateral aspect of the proximal tibial epiphysis

Explanation

Genu valgum is a classic orthopedic manifestation of Ellis-van Creveld syndrome. It is primarily caused by hypoplasia of the lateral aspect of the proximal tibial epiphysis and associated depression of the lateral tibial plateau.

Question 3766

Topic: 4. Pediatrics

Before proceeding with corrective orthopedic surgery for a patient with chondroectodermal dysplasia (Ellis-van Creveld syndrome), a thorough cardiology evaluation is mandatory. Which congenital cardiac anomaly is most characteristically associated with this syndrome?

. Ventricular septal defect
. Tetralogy of Fallot
. Common atrium (atrial septal defect)
. Coarctation of the aorta
. Transposition of the great arteries

Correct Answer & Explanation

. Common atrium (atrial septal defect)

Explanation

Approximately 50-60% of patients with Ellis-van Creveld syndrome have congenital heart disease. The most characteristic defect is an atrial septal defect, specifically a common atrium.

Question 3767

Topic: 4. Pediatrics

In patients with Ellis-van Creveld syndrome, the disproportionate short stature is primarily characterized by which of the following patterns of limb shortening?

. Rhizomelic
. Mesomelic and acromelic
. Asymmetric
. Diaphyseal
. Global, proportionate

Correct Answer & Explanation

. Mesomelic and acromelic

Explanation

The short-limb dwarfism seen in Ellis-van Creveld syndrome is predominantly mesomelic (middle segment) and acromelic (distal segment). This contrasts with achondroplasia, which is primarily rhizomelic.

Question 3768

Topic: 4. Pediatrics

When taking a family history from parents of a child suspected of having Ellis-van Creveld syndrome, recognizing population genetics is helpful. This autosomal recessive syndrome occurs with an unusually high frequency in which of the following populations due to a founder effect?

. Ashkenazi Jewish population
. Old Order Amish population in Pennsylvania
. Finnish population
. French-Canadian population
. South African Afrikaner population

Correct Answer & Explanation

. Old Order Amish population in Pennsylvania

Explanation

Ellis-van Creveld syndrome is exceptionally prevalent among the Old Order Amish population of Lancaster County, Pennsylvania, due to a founder effect and inbreeding. The carrier rate in this population is estimated to be up to 13%.

Question 3769

Topic: 4. Pediatrics

A 10-year-old patient with Ellis-van Creveld syndrome has progressive, symptomatic genu valgum secondary to lateral proximal tibial hypoplasia. The physes remain widely open. Which of the following is the most appropriate initial surgical intervention?

. Total knee arthroplasty
. Proximal tibial medial closing wedge osteotomy
. Guided growth via medial proximal tibial hemiepiphysiodesis
. Distal femoral lateral opening wedge osteotomy
. Resection of the proximal fibula

Correct Answer & Explanation

. Guided growth via medial proximal tibial hemiepiphysiodesis

Explanation

In a growing child with open physes and progressive genu valgum, guided growth via medial proximal tibial hemiepiphysiodesis is a minimally invasive and highly effective initial surgical option. It gradually corrects the angular deformity by temporarily tethering the medial physis while the lateral physis continues to grow.

Question 3770

Topic: 4. Pediatrics

A 5-year-old child of Amish descent presents with disproportionate short stature. In Ellis-van Creveld syndrome, which specific segments of the limbs are typically the most severely shortened?

. Proximal segment (rhizomelic)
. Middle segment only (mesomelic)
. Distal segment only (acromelic)
. Middle and distal segments (acromesomelic)
. Generalized and proportional shortening

Correct Answer & Explanation

. Middle and distal segments (acromesomelic)

Explanation

Ellis-van Creveld syndrome typically causes acromesomelic dwarfism. This means the shortening is most pronounced in the middle segments (forearm/leg) and distal segments (hands/feet), distinguishing it from the rhizomelic shortening seen in achondroplasia.

Question 3771

Topic: 4. Pediatrics

A 10-year-old girl with Ellis-van Creveld syndrome presents with progressive genu valgum and lateral patellar instability. What is the primary underlying anatomic basis for this characteristic knee deformity?

. Medial femoral condyle overgrowth
. Lateral tibial plateau hypoplasia
. Congenital patellar aplasia
. Anterior tibial bowing
. Proximal focal femoral deficiency

Correct Answer & Explanation

. Lateral tibial plateau hypoplasia

Explanation

The classic knee deformity in EVC syndrome is severe genu valgum driven by hypoplasia and depression of the lateral tibial plateau. This bony deficiency also leads to habitual lateral patellar subluxation or dislocation.

Question 3772

Topic: 4. Pediatrics

A newborn is diagnosed with Ellis-van Creveld syndrome. Approximately 50% of these infants do not survive infancy. What is the most frequent cause of mortality in the neonatal period for this syndrome?

. Cervical spine instability leading to cord compression
. Spontaneous intracranial hemorrhage
. Cardiorespiratory failure
. Overwhelming sepsis due to primary immunodeficiency
. End-stage renal disease from polycystic kidneys

Correct Answer & Explanation

. Cardiorespiratory failure

Explanation

Neonatal mortality in EVC syndrome is high, most commonly resulting from a combination of congenital heart defects (such as a single atrium/ASD) and respiratory insufficiency secondary to a narrow, dysplastic thorax.

Question 3773

Topic: 4. Pediatrics

An anteroposterior pelvic radiograph of an infant with suspected Ellis-van Creveld syndrome is obtained. Which of the following findings is most characteristic of this condition?

. Champagne glass appearance of the pelvic inlet
. Trident pelvis with inferior acetabular spurs
. Complete congenital absence of the symphysis pubis
. Coxa vara with a femoral neck-shaft angle of 90 degrees
. Severe bilateral developmental dysplasia of the hip with superior dislocation

Correct Answer & Explanation

. Trident pelvis with inferior acetabular spurs

Explanation

In infants with EVC, the pelvis frequently demonstrates a "trident" appearance due to the presence of central and lateral spur-like downward projections at the margins of the acetabula.

Question 3774

Topic: 4. Pediatrics

Radiographs of the hands of a 6-year-old child with Ellis-van Creveld syndrome are reviewed. Besides postaxial polydactyly, what unique phalangeal characteristic is highly characteristic?

. Delta phalanges of the thumb
. Bullet-shaped middle phalanges
. Cone-shaped epiphyses of the middle and proximal phalanges
. Avascular necrosis of the distal phalanges
. Complete congenital absence of the distal phalanges

Correct Answer & Explanation

. Cone-shaped epiphyses of the middle and proximal phalanges

Explanation

Cone-shaped epiphyses, particularly in the middle and proximal phalanges, are highly characteristic radiographic findings in the hands of patients with EVC, often leading to premature physeal closure.

Question 3775

Topic: 4. Pediatrics

A newborn presents with a narrow, bell-shaped thorax, short limbs, and postaxial polydactyly. Renal ultrasound reveals early cystic dysplasia, while an echocardiogram is strictly normal. Given the specific clinical overlap, which condition is the most likely alternative diagnosis to Ellis-van Creveld syndrome?

. Achondroplasia
. Jeune syndrome (Asphyxiating thoracic dystrophy)
. Cleidocranial dysplasia
. Osteogenesis imperfecta type II
. Diastrophic dysplasia

Correct Answer & Explanation

. Jeune syndrome (Asphyxiating thoracic dystrophy)

Explanation

Jeune syndrome shares features of a narrow thorax, short limbs, and occasionally polydactyly, making it a key differential for EVC. However, Jeune syndrome frequently features severe renal cysts/disease and lacks the high incidence of congenital heart defects seen in EVC.

Question 3776

Topic: 4. Pediatrics

What is the primary pathophysiological basis for the severe respiratory difficulties commonly observed in infants with Ellis-van Creveld syndrome?

. Tracheomalacia causing dynamic airway collapse
. Short ribs leading to a narrow, restrictive thorax
. Congenital diaphragmatic hernia
. Severe cervical kyphosis compressing the brainstem respiratory centers
. Primary pulmonary hypoplasia independent of skeletal development

Correct Answer & Explanation

. Short ribs leading to a narrow, restrictive thorax

Explanation

The chondrodystrophy in EVC affects the ribs, rendering them abnormally short. This results in a long, narrow, "bell-shaped" thorax that restricts lung expansion, causing secondary respiratory insufficiency.

Question 3777

Topic: 4. Pediatrics

A 4-year-old child presents with recurrent fractures, blue sclerae, and the radiographic findings shown.

Which of the following genes is most likely mutated in this patient?

. FGFR3
. COL1A1
. COMP
. RUNX2
. COL2A1

Correct Answer & Explanation

. COL1A1

Explanation

This patient has Osteogenesis Imperfecta (OI), characterized by recurrent fractures, deformity, and osteopenia. OI is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, leading to defective type I collagen synthesis.

Question 3778

Topic: 4. Pediatrics
A 7-year-old girl with severe Osteogenesis Imperfecta (Type III) presents with pronounced anterolateral bowing of the bilateral femurs precluding ambulation. What is the most appropriate surgical intervention?
. Pavlik harness application
. Spica casting
. Multi-level osteotomies with telescopic intramedullary rodding
. Plating with rigid internal fixation
. Unilateral external fixation

Correct Answer & Explanation

. Multi-level osteotomies with telescopic intramedullary rodding

Explanation

In severe Osteogenesis Imperfecta with long bone deformity, multi-level corrective osteotomies stabilized by telescopic (growing) intramedullary rods (e.g., Fassier-Duval) are the gold standard. Rigid plating or external fixation is avoided due to the poor bone quality and high risk of peri-implant fractures.

Question 3779

Topic: 4. Pediatrics

A 4-year-old boy presents with progressive bowing of the lower extremities. Laboratory evaluation reveals normal calcium, low phosphorus, elevated alkaline phosphatase, and normal parathyroid hormone levels. What is the most likely genetic mutation?

. PHEX
. FGFR3
. COL1A1
. CBFA1
. GNAS

Correct Answer & Explanation

. PHEX

Explanation

X-linked hypophosphatemic rickets is caused by a PHEX gene mutation, which leads to decreased degradation of FGF-23. Elevated FGF-23 causes profound renal phosphate wasting and impaired 1-alpha-hydroxylase activity.

Question 3780

Topic: 4. Pediatrics

A 6-year-old child with a known genetic disorder presents with recurrent femoral fractures and severe progressive anterolateral bowing.

What is the most definitive surgical treatment for this long bone deformity?

. Open reduction and rigid plate fixation
. Application of a multi-planar external fixator
. Multiple osteotomies and telescoping intramedullary rodding
. Spica casting until skeletal maturity
. Flexible intramedullary nailing without osteotomy

Correct Answer & Explanation

. Multiple osteotomies and telescoping intramedullary rodding

Explanation

The Sofield-Millar procedure, consisting of multiple osteotomies and the insertion of a telescoping intramedullary rod (e.g., Fassier-Duval), is the gold standard for long bone deformities in Osteogenesis Imperfecta. It prevents recurrent fractures while accommodating patient growth.

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