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 5981
Topic: 4. Pediatrics
A 9-year-old child presents with a waddling gait and aching leg pain. Radiographs show bilateral, symmetric cortical thickening of the femoral and tibial diaphyses with sparing of the epiphyses. Genetic testing is most likely to reveal a mutation in which gene?
Correct Answer & Explanation
. TGFB1
Explanation
The clinical and radiographic presentation is classic for progressive diaphyseal dysplasia (Camurati-Engelmann disease). This autosomal dominant condition is caused by mutations in the TGFB1 gene.
Question 5982
Topic: Pediatric Hip
A 14-year-old boy presents for evaluation of shoulder hypermobility. He is able to touch his shoulders together anteriorly. Examination reveals a large, open anterior fontanelle and retained deciduous teeth. He is at increased risk for developing which of the following orthopedic conditions?
Correct Answer & Explanation
. Coxa vara
Explanation
This patient has cleidocranial dysplasia (RUNX2 mutation), characterized by hypoplastic/absent clavicles, delayed fontanelle closure, and delayed dental eruption. Orthopedically, these patients have a high incidence of progressive developmental coxa vara.
Question 5983
Topic: 4. Pediatrics
An 8-year-old boy presents with a waddling gait and severe, deep, aching bone pain in both legs. Radiographs demonstrate symmetrical, dense cortical thickening of the bilateral femoral and tibial diaphyses, sparing the epiphyses.
Genetic testing would most likely reveal a mutation in which of the following genes?
Correct Answer & Explanation
. TGFB1
Explanation
The clinical and radiographic presentation is classic for Progressive Diaphyseal Dysplasia (Camurati-Engelmann disease). This condition is inherited in an autosomal dominant fashion and is caused by mutations in the TGFB1 gene.
Question 5984
Topic: 4. Pediatrics
In a patient with achondroplasia, what is the most common cause of sudden death in infancy or early childhood?
Correct Answer & Explanation
. Cervicomedullary compression at the foramen magnum
Explanation
Infants with achondroplasia have a narrowed foramen magnum due to abnormal endochondral ossification of the skull base. This stenosis can cause cervicomedullary compression, leading to central apnea and sudden death if not decompressed surgically.
Question 5985
Topic: 4. Pediatrics
A newborn is diagnosed with Spondyloepiphyseal Dysplasia congenita (SEDc). Which of the following best describes the underlying genetic defect and the typical associated clinical finding?
Correct Answer & Explanation
. COL2A1 mutation; severe myopia and retinal detachment
Explanation
SED congenita is caused by mutations in the COL2A1 gene, affecting Type II collagen production. Because Type II collagen is abundant in the vitreous humor of the eye, these patients frequently suffer from severe myopia and are at high risk for retinal detachment.
Question 5986
Topic: 4. Pediatrics
A 9-year-old boy with normal intelligence and normal facial features presents with joint pain and a waddling gait. Lateral radiographs of his knees reveal a 'double-layer' patella. What is the most likely diagnosis?
Correct Answer & Explanation
. Multiple Epiphyseal Dysplasia (MED)
Explanation
The 'double-layer' patella is a classic radiographic sign for Multiple Epiphyseal Dysplasia (MED). MED is most commonly caused by mutations in the Cartilage Oligomeric Matrix Protein (COMP) gene.
Question 5987
Topic: 4. Pediatrics
A 12-year-old boy complains of bilateral leg pain and a waddling gait. Radiographs show symmetrical cortical thickening of the bilateral femoral and tibial diaphyses, sparing the epiphyses.
Mutation in which of the following genes is responsible for this condition?
Correct Answer & Explanation
. TGFB1
Explanation
The patient's presentation and images are characteristic of Camurati-Engelmann disease (Progressive Diaphyseal Dysplasia). It is inherited in an autosomal dominant pattern and is caused by a mutation in the TGFB1 gene.
Question 5988
Topic: 4. Pediatrics
A 35-year-old patient presents with chronic, asymmetric limb pain and joint stiffness. Radiographs show dense, irregular cortical hyperostosis extending along the diaphysis of the femur, resembling 'dripping candle wax'. Which gene mutation is most commonly associated with this condition?
Correct Answer & Explanation
. LEMD3
Explanation
The described condition is melorheostosis, characterized radiographically by a 'dripping candle wax' appearance of the cortex. It is associated with a loss-of-function mutation in the LEMD3 gene.
Question 5989
Topic: 4. Pediatrics
A 3-year-old child presents with a short trunk, prominent chest, and coxa vara. Ophthalmologic exam reveals high myopia. Radiographs show delayed ossification of the epiphyses and platyspondyly. The genetic defect underlying this condition primarily affects which of the following?
Correct Answer & Explanation
. Type II collagen
Explanation
The clinical picture describes spondyloepiphyseal dysplasia congenita (SEDC), which is caused by a mutation in the COL2A1 gene. This affects Type II collagen, a major structural component of both articular cartilage and the vitreous humor.
Question 5990
Topic: 4. Pediatrics
A newborn is noted to have severe micromelia, bilateral clubfeet, hitchhiker thumbs, and swelling of the external ear auricles (cauliflower ears). Which of the following genes is mutated in this condition?
Correct Answer & Explanation
. SLC26A2
Explanation
Diastrophic dysplasia is an autosomal recessive disorder caused by a mutation in the SLC26A2 (DTDST) gene, which encodes a sulfate transporter. Hallmark features include hitchhiker thumbs, cauliflower ears, and severe clubfeet.
Question 5991
Topic: 4. Pediatrics
Which of the following radiographic features is most reliable for distinguishing a chondromyxoid fibroma from a chondroblastoma in the long bones of a skeletally immature patient?
Correct Answer & Explanation
. The anatomic location relative to the physis
Explanation
Anatomic location is a key differentiator: chondroblastomas classically arise in the epiphysis or apophysis, whereas chondromyxoid fibromas are typically eccentrically located in the metaphysis.
Question 5992
Topic: 4. Pediatrics
A 9-year-old boy presents with bilateral knee and hip pain after activity. He is of normal height but has a waddling gait. Radiographs show delayed, irregular ossification of the capital femoral epiphyses and a classic "double-layer" appearance of the patella on lateral knee radiographs. A mutation in which of the following genes is most likely?
Correct Answer & Explanation
. COMP
Explanation
The clinical presentation and classic "double-layer" patella strongly suggest Multiple Epiphyseal Dysplasia (MED). The most common mutation associated with MED is in the COMP (Cartilage Oligomeric Matrix Protein) gene, inherited in an autosomal dominant fashion.
Question 5993
Topic: 4. Pediatrics
A 4-year-old child presents with short trunk dwarfism, severe coxa vara, and myopia. Radiographs reveal delayed ossification of the pubic bones, knee epiphyses, and calcaneus. Which collagen type is primarily affected by the underlying genetic mutation in this disorder?
Correct Answer & Explanation
. Type II
Explanation
Spondyloepiphyseal dysplasia (SED) congenita is an autosomal dominant disorder caused by a mutation in the COL2A1 gene. This mutation specifically disrupts the formation of Type II collagen, which is critical for hyaline cartilage formation.
Question 5994
Topic: 4. Pediatrics
An infant is evaluated in the neonatal intensive care unit for severe short-limb dwarfism. Examination reveals bilateral severe rigid clubfeet, proximally placed "hitchhiker" thumbs, and cystic swelling of the bilateral pinnae. The underlying genetic defect involves an inability to properly transport which of the following?
Correct Answer & Explanation
. Sulfate
Explanation
The infant's presentation of cauliflower ears, hitchhiker thumbs, and clubfeet is diagnostic for diastrophic dysplasia. This condition is caused by a mutation in the SLC26A2 (DTDST) gene, which encodes a sulfate transporter, leading to undersulfation of proteoglycans in cartilage.
Question 5995
Topic: 4. Pediatrics
A 4-year-old boy with spastic diplegia presents with a severe scissoring gait. He has excellent head and trunk control. Examination shows hyperreflexia and clonus in the lower extremities but near-normal function in the upper extremities. If a selective dorsal rhizotomy (SDR) is considered, which of the following is the most appropriate indication for this procedure?
Correct Answer & Explanation
. Spasticity interfering with mobility in a patient with good underlying motor control
Explanation
Correct Answer: Spasticity interfering with mobility in a patient with good underlying motor controlSelective dorsal rhizotomy (SDR) involves the sectioning of sensory nerve rootlets in the spinal cord to reduce spasticity. The ideal candidate is a child with spastic diplegia, typically aged 3-8 years, with good underlying muscle strength, selective motor control, and cognitive function, where spasticity is the primary hindrance to mobility. It is contraindicated in patients with severe fixed contractures (who require orthopedic soft tissue releases or bony work), athetoid/dystonic CP, or poor underlying motor control where spasticity is actually required to maintain posture and stand.
Question 5996
Topic: 4. Pediatrics
A 4-year-old boy with spastic diplegic cerebral palsy presents for orthopedic evaluation. He is able to sit independently but requires a handheld mobility device to walk indoors. According to the Gross Motor Function Classification System (GMFCS), he is classified as Level III. What is the most appropriate hip surveillance protocol for this patient?
Correct Answer & Explanation
. AP pelvis radiograph every 6 to 12 months
Explanation
Hip displacement is a common and severe complication in children with cerebral palsy, directly correlating with their GMFCS level. Children classified as GMFCS Levels III, IV, and V are at the highest risk for progressive hip subluxation and dislocation. According to established hip surveillance guidelines (such as those by the AACPDM), these high-risk children should undergo clinical examination and an AP pelvis radiograph every 6 to 12 months to monitor the Reimers migration percentage. Waiting for pain is inappropriate, as hip displacement is often asymptomatic until severe degenerative changes or dislocation occur.
Question 5997
Topic: 4. Pediatrics
A 5-year-old boy with spastic diplegia exhibits a severe scissoring gait. Physical examination demonstrates significant spasticity of the hip adductors with a maximum hip abduction of 20 degrees bilaterally when the hips are extended. Which of the following muscles is the primary target for surgical release to address this specific gait abnormality?
Correct Answer & Explanation
. Adductor longus
Explanation
Correct Answer: CA scissoring gait in cerebral palsy is primarily caused by spasticity and contracture of the hip adductor musculature. The adductor longus is the most superficial and typically the most severely contracted muscle contributing to this deformity. Surgical management usually involves an adductor tenotomy, primarily targeting the adductor longus, and often the gracilis, to improve hip abduction, facilitate perineal hygiene, and prevent progressive hip subluxation. The iliopsoas contributes to flexion contractures, and the rectus femoris to stiff-knee gait.
Question 5998
Topic: 4. Pediatrics
A 4-year-old boy with spastic diplegic cerebral palsy presents with a severe scissoring gait. He has excellent head control but requires the use of his hands to support his trunk while sitting. Examination shows hyperreflexia and clonus in the lower extremities with near-normal upper extremity function. Which of the following is the most accurate predictor regarding his future ability to ambulate independently?
Correct Answer & Explanation
. Inability to sit independently without hand support by age 4
Explanation
Correct Answer: BThe ability to sit independently by age 2 is the most reliable prognostic indicator for future independent ambulation in children with cerebral palsy. If a child can sit independently by age 2, there is a high likelihood they will eventually walk. Conversely, if a child cannot sit independently by age 4 (as in this patient, who requires his hands to support his trunk), the prognosis for independent ambulation is very poor. While head control and upper extremity function are important developmental milestones, independent sitting is the classic and most strongly correlated milestone for predicting ambulation potential.
Question 5999
Topic: 4. Pediatrics
A 4-year-old boy with spastic diplegic cerebral palsy presents with a severe scissoring gait. He has excellent head control and is able to sit independently with his hands supporting his trunk. Physical examination demonstrates significant adductor spasticity, hyperreflexia, and clonus in the lower extremities, with near-normal upper extremity function. Radiographs show early lateral subluxation of both hips. Which of the following is the most appropriate surgical intervention to address his scissoring gait and prevent progressive hip displacement?
Correct Answer & Explanation
. Bilateral obturator neurectomies and adductor longus releases
Explanation
Correct Answer: AScissoring gait in a child with spastic diplegic cerebral palsy is primarily caused by severe spasticity and contracture of the hip adductors. This spasticity not only impairs gait and perineal hygiene but also places the hips at high risk for progressive subluxation and dislocation due to the unopposed adductor and flexor forces. In a young child (typically under 5-6 years of age) with severe scissoring and hips "at risk" (early subluxation), soft tissue releases are indicated. Bilateral adductor longus releases, often combined with anterior obturator neurectomies, effectively reduce the deforming forces, improve gait mechanics, and help stabilize the hips. Proximal femoral VDRO is typically reserved for older children with established bony dysplasia or more severe subluxation (migration percentage > 40-50%).
Question 6000
Topic: 4. Pediatrics
A 4-year-old child with spastic diplegia is being evaluated for hip subluxation. According to the Gross Motor Function Classification System (GMFCS), the child is classified as Level IV. What is the recommended frequency of radiographic hip surveillance for this patient?
Correct Answer & Explanation
. Every 6 months until age 7, then annually until skeletal maturity
Explanation
Children with cerebral palsy are at significant risk for progressive hip displacement (subluxation and dislocation) due to muscle spasticity and imbalance. The risk is directly correlated with the severity of motor impairment, as classified by the GMFCS. Children at GMFCS levels III, IV, and V are at the highest risk. Current hip surveillance guidelines recommend that for these high-risk patients, an anteroposterior (AP) pelvis radiograph should be obtained every 6 months from age 2 until age 7. After age 7, if the hips are stable, surveillance should continue annually until skeletal maturity. Early detection allows for soft tissue releases or bony reconstructive procedures before irreversible joint damage occurs.
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