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4. Pediatrics MCQs

Practice Set 41 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 801

Topic: Pediatric Hip
Which of the following is the most important prognostic factor in a patient with Legg-Calvé-Perthes disease?
. Age at the time of clinical onset
. Gender of the patient
. Duration of symptoms before diagnosis
. Presence of a positive Trendelenburg sign
. Body mass index

Correct Answer & Explanation

. Age at the time of clinical onset

Explanation

Age at clinical onset is the most critical prognostic factor in Legg-Calvé-Perthes disease. Children who develop the condition before 6 to 8 years of age have a better prognosis due to greater potential for acetabular remodeling.

Question 802

Topic: Pediatric Hip

What is the approximate rate of bilateral involvement in patients presenting with Slipped Capital Femoral Epiphysis (SCFE)?

. 5-10%
. 20-40%
. 60-80%
. 85-95%
. 100%

Correct Answer & Explanation

. 20-40%

Explanation

Bilateral involvement in SCFE occurs in 20-40% of cases, with up to half presenting simultaneously. Patients with endocrinopathies or who present at an atypically young age have an even higher risk of bilaterality.

Question 803

Topic: Pediatric Hip

In the Graf classification for developmental dysplasia of the hip (DDH) using ultrasound, what does the alpha angle measure?

. The cartilaginous roof coverage
. The bony acetabular roof concavity
. The dynamic instability of the femoral head
. The distance from the femoral head to the teardrop
. The version of the acetabulum

Correct Answer & Explanation

. The bony acetabular roof concavity

Explanation

The alpha angle in Graf's ultrasound evaluation measures the concavity of the bony acetabular roof. A normal alpha angle is typically greater than 60 degrees. The beta angle assesses the cartilaginous roof.

Question 804

Topic: 4. Pediatrics

Which of the following gene mutations is most commonly associated with Osteogenesis Imperfecta type I?

. COL1A1
. COL2A1
. FGFR3
. COMP
. RUNX2

Correct Answer & Explanation

. COL1A1

Explanation

Osteogenesis imperfecta type I is an autosomal dominant condition most commonly caused by mutations in the COL1A1 or COL1A2 genes. These mutations lead to a quantitative defect in type I collagen, resulting in bone fragility, blue sclerae, and hearing loss.

Question 805

Topic: 4. Pediatrics

A 3-year-old boy presents with disproportionate short stature, frontal bossing, and rhizomelic shortening. A radiograph is shown.

What is the underlying genetic mechanism for this condition?

. Gain-of-function mutation in FGFR3
. Loss-of-function mutation in FGFR3
. Mutation in COMP gene
. Defect in type X collagen
. Defect in sulfate metabolism

Correct Answer & Explanation

. Gain-of-function mutation in FGFR3

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene, which inhibits chondrocyte proliferation in the proliferative zone of the physis. This results in rhizomelic dwarfism, characteristic facial features, and spinal stenosis.

Question 806

Topic: 4. Pediatrics

A 3-year-old child presents with an obvious right lower extremity abnormality. The left lower extremity has normal alignment and joint function. The right lower extremity displays a severely short thigh with a flexed hip. The right foot and leg are also abnormal. Radiographs reveal a right proximal femur with no femoral head or neck, as well as acetabular dysplasia. There is also fibular hemimelia and two missing lateral rays of the foot. The parents want treatment to preserve the function of the normal leg. The most appropriate treatment is:

. Observation
. Right Syme's amputation with knee fusion and prosthetic fitting
. Van Nes rotation-plasty
. Femoral lengthening
. Equinus prosthesis

Correct Answer & Explanation

. Right Syme's amputation with knee fusion and prosthetic fitting

Explanation

According to the Aitken classification, the patient has a type C proximal femoral focal deficiency (PFFD). In addition to a severe leg length discrepancy, a dysfunctional foot and ankle are also present. The patient would be best suited with an operative procedure to allow the development of ambulatory skills. The Syme's amputation with knee fusion is the standard procedure for severe PFFD and allows the patient to become proficient in the use of a prosthesis at an early age. In a child this young, a rotation-plasty may not be the best option due to a propensity to de-rotate and the weakness of the underdeveloped right ankle. For severe PFFD with unstable or dysplastic joints, lengthening is not the best option. If the leg length discrepancy were predicted to be <20 cm and a hip joint were present, then lengthening would be a better choice. If the child had a mild leg length discrepancy and was a candidate for lengthening, then an equinus prosthesis would be a reasonable choice until appropriate age for lengthening.

Question 807

Topic: 4. Pediatrics

The most common associated abnormality with proximal femoral focal deficiency (PFFD) is:

. Tibial hemimelia
. Fibular hemimelia
. Absent radius
. Congenital scoliosis
. Cardiac defects

Correct Answer & Explanation

. Fibular hemimelia

Explanation

Up to 45% of proximal femoral focal deficiency (PFFD) cases have coexisting fibular hemimelia. Tibial hemimelia may also have associated abnormalities of the distal femoral physis leading to a varus knee, but PFFD is more common. Absent radius is typically associated with thrombocytopenia agenesis radius (TAR) syndrome. Congenital scoliosis and cardiac defects are not commonly reported with PFFD.

Question 808

Topic: 4. Pediatrics

Genetic transmission of osteogenesis imperfecta (OI) is best described as:

. Autosomal dominant
. Autosomal recessive
. Sex-linked dominant
. Autosomal dominant and autosomal recessive
. Not genetically transmitted

Correct Answer & Explanation

. Autosomal dominant and autosomal recessive

Explanation

Depending on the particular mutation involved, osteogenesis imperfecta can be either autosomal dominant or autosomal recessive. Osteogenesis imperfecta occurs because of a defect in type I collagen. The genes for type I collagen are found on chromosomes 7 and 17, and are therefore not sex- linked.

Question 809

Topic: 4. Pediatrics

The most common neurologic complications of osteogenesis imperfecta (OI) is:

. Intracranial hemorrhage
. Subdural hematoma
. Brainstem compression
. Mental retardation
. Herniated nucleus pulposes

Correct Answer & Explanation

. Brainstem compression

Explanation

Basilar impression with brainstem compression is a neurologic sequela of the deforming types of osteogenesis imperfecta (OI). It can be identified by noting that the tip of the dens projects 7 mm or more above McGregor's line on plain film.

Question 810

Topic: Pediatric Lower Extremity

Fibular hemimelia (FH) can be associated with which of the following abnormalities:

. Femoral shortening
. Anterior cruciate ligament (AC L) deficiency
. Equinovalgus foot
. Tarsal coalition
. All of the above

Correct Answer & Explanation

. All of the above

Explanation

All of the stated abnormalities can be found with femoral hemimelia. It is estimated that 15% of cases have femoral deficiency. Commonly seen in the condition are tarsal coalition, anterior cruciate ligament deficiency, and an equinovalgus foot.

Question 811

Topic: 4. Pediatrics
The most common presenting symptoms of congenital pseudarthrosis of the clavicle are:
. Enlarging mass and history of pseudoparalysis at birth
. Refusal to use arm, palpable defect, and pain
. Minimally painful or painless prominence with no history of trauma
. Limitation of abduction to less than or equal to 90°
. Weakness in the distribution of the upper trunk of the brachial plexus

Correct Answer & Explanation

. Minimally painful or painless prominence with no history of trauma

Explanation

The most common presentation of pseudarthrosis of the clavicle is a painless mass in the clavicle. There is no history of trauma, and the child uses the extremity normally, with minimal pain, and with no signs of instability. There is no history of pseudoparalysis involved with congenital pseudarthrosis. Arm use is nearly normal, except for aching with activity. There is minimal restriction of motion with the pseudarthrosis, which is one reason it is sometimes not diagnosed until later in childhood. There has not been neurologic impairment with this condition.

Question 812

Topic: 4. Pediatrics

Which of the following statements regarding congenital pseudarthrosis of the clavicle is not true:

. C ongenital pseudarthrosis of the clavicle occurs primarily on the right, rarely bilaterally, and when occurring on the left, congenital pseudarthrosis of the clavicle is usually associated with dextrocardia.
. Congenital pseudarthrosis of the clavicle is strongly associated with neurofibromatosis and patients often have other pseudarthroses, with the tibia being the most commonly affected site.
. Congenital pseudarthrosis of the clavicle is thought to occur due to pressure on the clavicle from the subclavian artery or prominent cervical ribs.
. Treatment for congenital pseudarthrosis of the clavicle involves intercalary bone grafting, plate, and screws.
. Impairment of the upper trunk of the brachial plexus rarely develops over time.

Correct Answer & Explanation

. Treatment for congenital pseudarthrosis of the clavicle involves intercalary bone grafting, plate, and screws.

Explanation

Pseudarthrosis of the clavicle occurs primarily on the right side. The right predominance has been attributed to pressure on the right clavicle from the subclavian artery and occasionally cervical ribs. Treatment is straightforward with intercalary bone grafting with plate and screws fixation. There is no association with neurofibromatosis and/or pseudarthrosis of the tibia. Unlike pseudarthrosis of the tibia, congenital pseudarthrosis of the clavicle is rarely, if ever, associated with neurofibromatosis Pressure from the subclavian artery or prominent cervical ribs have been used to explain the observation that the pseudarthrosis is almost always located on the right, and if bilateral, it is associated with bilateral cervical ribs Bone graft with plate fixation is the usual treatment for these cases, although there have been reports of success in younger children from simply suturing the periosteum of the two ends together Brachial plexus impairment rarely develops in the untreated pseudarthrosis.

Question 813

Topic: 4. Pediatrics

Which of the following statements is true regarding Lyme disease:

. C ardiac and neurologic symptoms are the most common manifestations of the disease.
. Arthritic symptoms primarily affect large joints and a majority of patients are cured with antibiotic therapy.
. The characteristic skin rash occurs late in the disease and can be permanently disfiguring.
. Arthritic symptoms often do not fully resolve with antibiotic treatment, with a majority of patients progressing on to a rheumatoid-like destructive arthritis.
. Lyme disease is easy to diagnose and a majority of cases are picked up after a few weeks.

Correct Answer & Explanation

. Arthritic symptoms primarily affect large joints and a majority of patients are cured with antibiotic therapy.

Explanation

Approximately 60% of patients develop arthritic symptoms that primarily affect large joints. The prognosis for most patients is good after treatment with antibiotics. Cardiac and neurologic symptoms occur in a minority of patients, however, they can be the most serious symptoms. Erythema chronicum migrans is the characteristic skin rash. The rash tends to remit with antibiotic treatment and permanent disfigurement is not typically a problem. Only 1%-2% of pediatric patients develop chronic arthritis. Lyme disease may be difficult to diagnose because of the numerous possible presentations.

Question 814

Topic: 4. Pediatrics

Patients with homocystinuria phenotypically resemble patients with:

. Achondroplasia
. Larsen's syndrome
. Marfan syndrome
. Gaucher's disease
. Noonan's syndrome

Correct Answer & Explanation

. Marfan syndrome

Explanation

Patients with homocystinuria may phenotypically resemble patients with Marfan syndrome. Patients with homocystinuria and Marfan syndrome are tall with long limbs, arachnodactyly, scoliosis, chest wall deformities, and lens dislocations. Achondroplasia is characterized by short stature, frontal bossing, and rhizomelic shortening of the limbs. Larsen's syndrome is a disorder characterized by short stature and multiple joint dislocations. Gaucher's disease is a lysosomal storage disease characterized by accumulation of cerebroside in cells of the reticuloendothelial system. As in patients with homocystinuria, patients with Gaucher's disease have osteoporosis, however, they do not develop any of the other phenotypic features seen in homocystinuria. Noonan's syndrome effects boys and clinical features include short stature, a webbed neck, and cubitus valgus deformities.

Question 815

Topic: 4. Pediatrics
A genetic defect found in some types of Ehlers-Danlos syndrome (EDS) is:
. Fibrillin
. Type I collagen
. Fibroblast growth factor (FGF) receptor 3
. Dystrophin
. Hypoxanthine-guanine phosphoribosyl transferase

Correct Answer & Explanation

. Type I collagen

Explanation

Ehlers-Danlos syndrome (EDS) was once described as a single gene disorder affecting type I collagen, but it has since been discovered that EDS is a family of heterogeneous disorders with many described mutations. Type I collagen is defective in EDS type VII and collagen type III is defective in EDS type IV and VIII. Fibrillin and fibroblast growth factor (FGF) receptor 3 are defective in Marfan syndrome and achondroplasia, respectively. Dystrophin is deficient in muscular dystrophy. Hypoxanthine-guanine phosphoribosyl transferase is defective in Lesch-Nyhan syndrome.

Question 816

Topic: Pediatric Hip

A 12-year-old male presents with a stable slipped capital femoral epiphysis (SCFE) of the left hip. Which of the following is the strongest clinical indication for prophylactic in situ pinning of the asymptomatic contralateral right hip?

. Age older than 14 years
. Female gender
. Presence of an endocrine disorder
. Presence of an ipsilateral joint effusion
. BMI less than 25

Correct Answer & Explanation

. Presence of an endocrine disorder

Explanation

Endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) significantly increase the risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly recommended in these patients.

Question 817

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls on an outstretched hand, sustaining a Gartland Type III extension-type supracondylar humerus fracture. Which nerve is most commonly injured in this specific fracture pattern?
. Ulnar nerve
. Radial nerve
. Anterior interosseous nerve (AIN)
. Posterior interosseous nerve (PIN)
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve (AIN)

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most frequently injured nerve in extension-type supracondylar humerus fractures. Clinically, this presents as an inability to make the "OK" sign.

Question 818

Topic: Pediatric Hip

A 4-month-old female infant is diagnosed with developmental dysplasia of the hip (DDH). Dynamic ultrasound confirms a dislocated but reducible left hip. What is the most appropriate initial management for this patient?

. Closed reduction and spica casting
. Open reduction and capsulorrhaphy
. Pavlik harness application
. Rigid hip abduction orthosis
. Observation and repeat ultrasound in 4 weeks

Correct Answer & Explanation

. Pavlik harness application

Explanation

For infants under 6 months of age with a reducible dislocated hip, a Pavlik harness is the gold standard initial treatment. It maintains the hip in flexion and abduction to promote concentric reduction and acetabular remodeling.

Question 819

Topic: Pediatric Hip
A 12-year-old boy diagnosed with slipped capital femoral epiphysis (SCFE) of the left hip undergoes in situ single-screw fixation. Prophylactic pinning of the asymptomatic contralateral right hip is most strongly indicated if the patient has which of the following?
. A body mass index (BMI) greater than the 95th percentile
. An underlying endocrine disorder or renal osteodystrophy
. A severe (Grade III) slip on the symptomatic side
. A history of previous developmental dysplasia of the hip (DDH)
. A chronologic age of 14 years or older

Correct Answer & Explanation

. An underlying endocrine disorder or renal osteodystrophy

Explanation

Prophylactic pinning of the contralateral hip in SCFE is highly recommended for patients with underlying endocrine disorders (e.g., hypothyroidism) or renal failure. These patients have a significantly higher risk of bilateral involvement compared to idiopathic cases.

Question 820

Topic: Pediatric Hip

When evaluating an infant with suspected developmental dysplasia of the hip (DDH) using coronal ultrasound, the alpha angle is measured. What does the alpha angle represent, and what is its normal value?

. Measures the cartilaginous roof and should be less than 55 degrees
. Measures the percentage of femoral head coverage and should be greater than 50 percent
. Measures the bony acetabular roof and should be greater than 60 degrees
. Measures the acetabular anteversion and should be greater than 20 degrees
. Measures the labral inversion angle and should be less than 43 degrees

Correct Answer & Explanation

. Measures the bony acetabular roof and should be greater than 60 degrees

Explanation

In the Graf method of neonatal hip ultrasound, the alpha angle quantifies the bony concavity of the acetabulum (bony roof). An alpha angle of greater than 60 degrees is considered normal (Graf Type I).

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