Menu

4. Pediatrics MCQs

Practice Set 216 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 4301

Topic: 4. Pediatrics

A 12-year-old non-ambulatory male with SMA Type II presents with bilateral 30-degree knee flexion contractures and 20-degree hip flexion contractures. His parents inquire about surgical release to allow him to lie completely flat in bed. He currently has no pain and sits comfortably in his wheelchair. What is the most appropriate recommendation?

. Immediate bilateral multilevel soft tissue releases of the hips and knees
. Botulinum toxin injections to the hamstrings and iliopsoas
. Bilateral distal femoral anterior closing-wedge extension osteotomies
. Observation and physical therapy, as surgery is rarely indicated for positioning alone in non-ambulators without pain
. Serial casting of the lower extremities over 6 weeks to achieve full extension

Correct Answer & Explanation

. Observation and physical therapy, as surgery is rarely indicated for positioning alone in non-ambulators without pain

Explanation

In non-ambulatory patients with SMA, mild to moderate flexion contractures of the hips and knees are very common and are often adaptively useful for stable sitting in a wheelchair. Surgical release is generally contraindicated for cosmetic reasons or just to lie flat, as it does not improve function, has a high recurrence rate, and subjects the medically fragile child to surgical risk. Surgery is reserved for severe pain, inability to sit, or skin breakdown.

Question 4302

Topic: 4. Pediatrics

Blue sclerae, a hallmark clinical finding in many patients with Osteogenesis Imperfecta (especially Type I), are primarily attributed to which of the following physiological alterations?

. Accumulation of unmineralized osteoid tissue in the sclera
. Deposition of hemosiderin pigments from recurrent microscopic conjunctival hemorrhages
. Thinning of the scleral collagen fibers revealing the underlying pigmented uvea/choroid
. A concomitant pleiotropic mutation in the PAX6 gene
. Hypervascularity of the deep episcleral plexus secondary to chronic inflammation

Correct Answer & Explanation

. Thinning of the scleral collagen fibers revealing the underlying pigmented uvea/choroid

Explanation

The sclera is normally composed of densely packed, thick type I collagen fibers that appear white. In OI, defective or deficient type I collagen leads to a globally thinner and more transparent sclera. This transparency allows the dark pigment of the underlying uveal tract (specifically the choroid) to show through, creating the characteristic blue or slate-gray appearance of the eyes.

Question 4303

Topic: 4. Pediatrics
A 2-month-old infant is diagnosed with SMA Type I (Werdnig-Hoffmann disease). The parents ask about Onasemnogene abeparvovec (Zolgensma). What is the mechanism of this therapy?
. Antisense oligonucleotide altering SMN2 splicing
. Small molecule oral SMN2 splicing modifier
. AAV9 viral vector delivering a fully functional SMN1 gene
. Monoclonal antibody against myostatin
. CRISPR-Cas9 targeted deletion of the mutated SMN1 gene

Correct Answer & Explanation

. AAV9 viral vector delivering a fully functional SMN1 gene

Explanation

Zolgensma is a gene replacement therapy that uses an adeno-associated virus serotype 9 (AAV9) vector to deliver a functional copy of the SMN1 gene. It is administered as a one-time intravenous infusion.

Question 4304

Topic: 4. Pediatrics

A newborn presents with hypotonia, multiple congenital fractures, and profound osteopenia on radiographs. Genetic testing confirms a mutation affecting type I collagen synthesis. The primary biochemical defect in classical Osteogenesis Imperfecta usually involves the substitution of which amino acid in the collagen triple helix?

. Proline
. Lysine
. Hydroxyproline
. Glycine
. Glutamate

Correct Answer & Explanation

. Glycine

Explanation

Type I collagen consists of a triple helix with a repeating Gly-X-Y amino acid sequence. Mutations causing substitution of the bulky glycine residue disrupt the tight coiling of the helix, causing classical (Type I-IV) Osteogenesis Imperfecta.

Question 4305

Topic: 4. Pediatrics

Which of the following accurately describes the pathology of the dental abnormalities commonly seen in classical Osteogenesis Imperfecta?

. Defective enamel formation due to an amelogenin mutation
. Obliteration of the pulp cavity and defect in dentin due to Type I collagen mutation
. Hypercementosis of the tooth roots due to excessive calcium deposition
. Failure of primary tooth eruption due to dense alveolar bone
. Severe gingival hyperplasia obscuring normal dentition

Correct Answer & Explanation

. Obliteration of the pulp cavity and defect in dentin due to Type I collagen mutation

Explanation

Dentinogenesis imperfecta in OI is caused by the same type I collagen defect affecting bone. It leads to defective dentin, rapid tooth wear, opalescent discoloration, and characteristic obliteration of the pulp chambers on dental radiographs.

Question 4306

Topic: 4. Pediatrics

You are examining an infant with multiple rib fractures in various stages of healing. You are trying to differentiate non-accidental trauma from Osteogenesis Imperfecta. Which skull radiograph finding strongly suggests Osteogenesis Imperfecta over abuse?

. A linear, non-displaced parietal fracture
. Presence of more than 10 Wormian bones in the lambdoid suture
. Premature closure of the sagittal suture
. Enlarged diploic space
. Basilar skull fracture

Correct Answer & Explanation

. Presence of more than 10 Wormian bones in the lambdoid suture

Explanation

Wormian bones are accessory bones within the cranial sutures. While a few can be normal, the presence of numerous (>10) or large Wormian bones is a classic radiographic sign of Osteogenesis Imperfecta and helps distinguish it from non-accidental trauma.

Question 4307

Topic: 4. Pediatrics

In a patient with Osteogenesis Imperfecta undergoing intramedullary rodding of the femur, which of the following osteotomy principles is critical to prevent the "Z-effect" or loss of fixation?

. Performing a single distal osteotomy regardless of deformity curve
. Creating multiple step-cut osteotomies to shorten the bone
. Ensuring the osteotomies allow the bone segments to be threaded centrally on the rod
. Using a purely cortical rigid nail rather than an elastic nail
. Placing the osteotomy strictly in the metaphyseal bone

Correct Answer & Explanation

. Ensuring the osteotomies allow the bone segments to be threaded centrally on the rod

Explanation

To correct severe bowing in OI, multiple osteotomies ("shish kebab" technique) are often required. It is critical that each bone segment is threaded centrally over the intramedullary rod to align the mechanical axis and prevent angulation or cut-out.

Question 4308

Topic: 4. Pediatrics

A newborn presents with a soft, fragile calvarium, a small thoracic cage, and severe bowing of all extremities. Radiographs reveal multiple fractures in various stages of healing, including "accordion" ribs. The infant succumbs to respiratory failure within 24 hours. According to the Sillence classification, what is the most likely fundamental genetic defect?

. Decreased quantity of structurally normal Type I collagen
. Qualitative defect due to a missense mutation in COL1A1 or COL1A2
. Quantitative defect due to a null allele in COL2A1
. Defect in the dentin sialophosphoprotein (DSPP) gene
. Defect in the SMN1 gene leading to anterior horn cell apoptosis

Correct Answer & Explanation

. Qualitative defect due to a missense mutation in COL1A1 or COL1A2

Explanation

This clinical picture describes Osteogenesis Imperfecta (OI) Type II, which is perinatally lethal. It is typically caused by a qualitative defect (missense mutation substituting glycine) in the COL1A1 or COL1A2 genes, creating a dominant negative effect.

Question 4309

Topic: 4. Pediatrics

A 7-year-old non-ambulatory child with Spinal Muscular Atrophy Type II presents for a routine orthopedic follow-up. Pelvic radiographs reveal a painless, complete lateral dislocation of the left hip. The child has no difficulty sitting in his wheelchair. What is the most appropriate management?

. Open reduction and Dega osteotomy
. Varus derotational osteotomy (VDRO)
. Observation and reassurance
. Application of a hip spica cast
. Bilateral adductor tenotomies

Correct Answer & Explanation

. Observation and reassurance

Explanation

Hip dislocations in non-ambulatory SMA patients are typically painless and do not interfere with sitting or quality of life. Surgical reduction has a high recurrence rate and is generally not recommended unless there is severe pain.

Question 4310

Topic: 4. Pediatrics
A 4-year-old girl with osteogenesis imperfecta type III requires surgical stabilization of a recurrent femur fracture. The surgeon elects to use a Fassier-Duval intramedullary nail. What is the primary biomechanical advantage of this device compared to a standard Rush rod?
. It provides rigid rotational control without locking screws
. Its telescoping design elongates with longitudinal bone growth
. It stimulates endosteal bone formation via micromotion
. It completely halts physeal growth to prevent bowing
. It relies purely on cortical engagement for stabilization

Correct Answer & Explanation

. Its telescoping design elongates with longitudinal bone growth

Explanation

The Fassier-Duval nail is a telescoping intramedullary device fixed at both the proximal and distal epiphyses. As the child grows, the rod elongates, providing continuous support and reducing the need for repeated surgeries due to bone outgrowing the rod.

Question 4311

Topic: 4. Pediatrics

A 6-month-old infant is newly diagnosed with SMA Type I. The family is counseled regarding Onasemnogene abeparvovec (Zolgensma) therapy. What is the fundamental mechanism of this treatment?

. Modifies pre-mRNA splicing of the SMN2 gene
. Antisense oligonucleotide that degrades mutant SMN1 mRNA
. An AAV9 viral vector delivering a fully functional human SMN1 gene
. Blocks neuromuscular junction acetylcholine receptors
. Inhibits the breakdown of SMN protein in the proteasome

Correct Answer & Explanation

. An AAV9 viral vector delivering a fully functional human SMN1 gene

Explanation

Zolgensma (Onasemnogene abeparvovec) is an adeno-associated virus (AAV9) vector-based gene therapy. It delivers a functional, episomal copy of the human SMN1 gene to motor neurons, addressing the root cause of SMA.

Question 4312

Topic: 4. Pediatrics
A 6-year-old boy with osteogenesis imperfecta type III presents with brownish-blue, opalescent teeth that exhibit significant wear and enamel flaking. This dental abnormality is a result of a defect in which of the following structures?
. Amelogenin
. Enamel matrix
. Dentin matrix
. Periodontal ligament
. Cementum

Correct Answer & Explanation

. Dentin matrix

Explanation

The patient has dentinogenesis imperfecta, commonly seen in OI. It occurs because the abnormal type I collagen structurally weakens the dentin matrix, causing the overlying normal enamel to flake off and exposing the discolored dentin.

Question 4313

Topic: 4. Pediatrics

A 10-year-old with Osteogenesis Imperfecta Type IV undergoes an osteotomy to correct severe anterior bowing of the tibia. Which of the following best characterizes the expected bone healing process in this patient compared to a healthy, age-matched child?

. Healing is significantly delayed, requiring twice the normal time
. Fracture healing occurs at a normal rate, but the resultant callus is mechanically weak
. The osteotomy will reliably proceed to nonunion without bone grafting
. Healing occurs primarily via endochondral ossification without a cartilaginous intermediate
. Hypertrophic nonunion is the standard outcome due to excessive micromotion

Correct Answer & Explanation

. Fracture healing occurs at a normal rate, but the resultant callus is mechanically weak

Explanation

In Osteogenesis Imperfecta, the physiological timeline of fracture healing is normal, and callus forms appropriately. However, the resulting bone remains mechanically compromised due to the underlying qualitative or quantitative defect in Type I collagen.

Question 4314

Topic: 4. Pediatrics

A 4-month-old infant is brought to the clinic for delayed motor milestones. Examination reveals severe hypotonia, a weak cry, "bell-shaped" chest, absent deep tendon reflexes, and distinct fasciculations of the tongue. The mother reports feeling diminished fetal movements during the third trimester. What is the most likely diagnosis?

. Duchenne Muscular Dystrophy
. Spinal Muscular Atrophy Type I
. Cerebral Palsy
. Charcot-Marie-Tooth Disease
. Becker Muscular Dystrophy

Correct Answer & Explanation

. Spinal Muscular Atrophy Type I

Explanation

This is the classic presentation of Werdnig-Hoffmann disease (SMA Type I). Hallmark features include severe hypotonia, areflexia, tongue fasciculations, and paradoxical breathing due to intercostal weakness with a spared diaphragm.

Question 4315

Topic: 4. Pediatrics

A 25-year-old woman with a history of mild Osteogenesis Imperfecta (Type I) presents for an orthopedic evaluation of a recent Colles fracture. Which of the following extraskeletal manifestations is most frequently associated with her condition and often becomes symptomatic during adulthood?

. Retinal detachment
. Sensorineural and/or conductive hearing loss
. Aortic root dilation
. Renal calculi
. Spontaneous pneumothorax

Correct Answer & Explanation

. Sensorineural and/or conductive hearing loss

Explanation

Hearing loss is a common extraskeletal manifestation of OI, particularly Type I, affecting roughly 50% of adult patients. It typically presents in the second or third decade and can be conductive, sensorineural, or mixed.

Question 4316

Topic: 4. Pediatrics
A 14-year-old girl is diagnosed with mild osteogenesis imperfecta (type I) after sustaining multiple fractures from minor trauma. Genetic analysis reveals a premature stop codon in one allele of COL1A1. What is the precise biochemical consequence of this mutation?
. Decreased quantity of structurally normal type I collagen
. Formation of an abnormal triple helix that degrades rapidly
. Complete absence of type III collagen
. Substitution of bulky amino acids for glycine in the alpha chains
. Defective cleavage of procollagen C-propeptides

Correct Answer & Explanation

. Decreased quantity of structurally normal type I collagen

Explanation

OI type I is typically caused by a null allele (e.g., a premature stop codon) in COL1A1, leading to haploinsufficiency. This results in a 50% decreased quantity of structurally normal type I collagen, causing a milder phenotype.

Question 4317

Topic: 4. Pediatrics

An infant diagnosed with SMA Type I receives Onasemnogene abeparvovec (Zolgensma) at 2 months of age. What is the mechanism by which this therapy provides a therapeutic benefit?

. It modifies the splicing of SMN2 pre-mRNA to increase functional SMN protein production.
. It delivers a fully functional copy of the human SMN1 gene using an adeno-associated virus (AAV9) vector.
. It acts as a neuroprotective agent blocking apoptosis of lower motor neurons.
. It replaces defective muscle fibers with healthy, laboratory-grown satellite cells.
. It inhibits the breakdown of acetylcholine in the neuromuscular junction.

Correct Answer & Explanation

. It delivers a fully functional copy of the human SMN1 gene using an adeno-associated virus (AAV9) vector.

Explanation

Onasemnogene abeparvovec is a gene replacement therapy. It utilizes a non-replicating AAV9 vector to deliver a functional copy of the SMN1 gene directly to the motor neurons.

Question 4318

Topic: 4. Pediatrics

A 6-year-old child with Osteogenesis Imperfecta undergoes bilateral femur Sofield-Millar osteotomies stabilized with Fassier-Duval telescoping rods. Which of the following is the most common complication specifically associated with this type of instrumentation?

. Nonunion of the osteotomy sites
. Deep surgical site infection
. Rod migration or failure to telescope
. Fat embolism syndrome
. Malignant degeneration of the callus

Correct Answer & Explanation

. Rod migration or failure to telescope

Explanation

Fassier-Duval rods are designed to elongate as the child grows. The most common complication is mechanical failure, specifically rod migration (backing out proximally or penetrating the joint distally) or failure of the components to telescope.

Question 4319

Topic: 4. Pediatrics
Which type of osteogenesis imperfecta, according to the Sillence classification, is characterized by extreme bone fragility, multiple intrauterine fractures, severe skeletal deformities, and is generally lethal in the perinatal period?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

OI type II is the most severe form and is considered perinatal lethal. It is characterized by severe bone deformity, multiple intrauterine rib and long bone fractures, and underdeveloped lungs leading to respiratory failure.

Question 4320

Topic: 4. Pediatrics

A pediatric patient with Spinal Muscular Atrophy Type II is evaluated in the clinic. Without disease-modifying therapies, what is the maximum expected motor milestone this patient will achieve during their natural history?

. Never gains head control
. Sits independently but never walks independently
. Walks with assistive devices but loses the ability by adolescence
. Walks independently throughout adulthood
. Achieves normal motor milestones but experiences late-onset weakness

Correct Answer & Explanation

. Sits independently but never walks independently

Explanation

Historically, without novel medical therapies, patients with SMA Type II can achieve the ability to sit independently but never achieve independent ambulation.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page