1. General Principles & Basic Science MCQs

A 6-year-old child presents with frequent fractures, anemia, and cranial nerve palsies. Radiographs demonstrate uniformly dense bones with a "bone-within-bone" appearance. A defect in which cell type is primarily responsible for this disorder?

A patient presents with absent clavicles, delayed closure of cranial sutures, and supernumerary teeth. What gene mutation is associated with this disorder?

A 45-year-old male presents with severe knee catching and locking. Radiographs and subsequent MRI reveal multiple calcific bodies within the joint space.

What radiographic feature best distinguishes primary synovial chondromatosis from secondary causes such as severe osteoarthritis?

A 10-year-old child presents with a waddling gait and knee pain. Radiographs demonstrate delayed, irregular epiphyseal ossification centers in the large joints, but the spine is entirely normal. Mutations in which of the following genes are most commonly responsible for the autosomal dominant form of this condition?

A 15-year-old male is referred for delayed tooth eruption and unusual shoulder mobility, allowing him to approximate his shoulders anteriorly at the midline. The primary genetic defect (CBFA1/RUNX2) in this condition impairs which of the following biological processes?

Radiographs of an infant reveal severe stippling of the epiphyses (chondrodysplasia punctata). A careful maternal history should be taken, as which teratogenic exposure produces a clinical phenocopy of this condition?

A 40-year-old man presents with a slowly enlarging, nodular violaceous plaque on his chest wall. Pathology reveals a cellular spindle cell proliferation arranged in a dense "storiform" pattern, infiltrating deeply into the subcutaneous fat in a honeycomb pattern. What genetic aberration drives this neoplasm?

A 35-year-old female presents with chronic, severe pain and stiffness in her right lower extremity. Radiographs show dense, irregular, eccentric hyperostosis along the cortex of the femur and tibia, resembling 'dripping candle wax'. What is the most likely diagnosis?

A 30-year-old patient with polyostotic fibrous dysplasia complains of severe, persistent bone pain in the lower extremities that limits daily activities. Surgical intervention is not currently indicated for structural reasons. Which of the following pharmacological therapies has the best evidence for reducing bone pain in this condition?

A 30-year-old patient presents with severe, deep, aching pain and progressive joint contractures in the lower extremity. Radiographs reveal dense, eccentric, undulating cortical hyperostosis extending along the length of the femur and tibia, resembling 'dripping candle wax'. What is the most likely diagnosis?

A 30-year-old male presents with severe, deep, aching pain and progressive joint contracture in his left lower extremity. Radiographs demonstrate dense, irregular, eccentric hyperostosis along the cortex of the femur and tibia, resembling 'dripping candle wax'. Which of the following is the most likely genetic mutation associated with this condition?

In a patient with Ollier disease, the characteristic skeletal lesions are primarily a result of which of the following pathophysiological processes?

A 35-year-old woman presents with chronic, deep aching pain in her right lower extremity and decreased range of motion in her knee. Radiographs reveal dense, irregular, eccentric hyperostosis along the cortex of the femur and tibia, resembling 'dripping candle wax'. Which of the following is the most likely diagnosis?

A 5-year-old child presents with a "hitchhiker" thumb, bilateral rigid clubfeet, and cauliflower ears. Radiographs reveal short, thick tubular bones. Which of the following genes is most likely mutated in this patient?

A 3-year-old is being evaluated for short stature, frontal bossing, and delayed closure of cranial sutures. The clavicles are completely absent on chest radiographs. Which transcription factor is primarily affected in this disorder?

A neonate presents with multiple fractures, blue sclerae, and profound osteopenia. The parents are carriers of a severe recessive form of this disease. Which of the following best describes the fundamental defect in the most common dominant forms of this condition?

A 4-year-old boy presents with knock-knees and short stature. Labs show normal serum calcium, normal phosphorus, normal alkaline phosphatase, and normal vitamin D levels. Radiographs show coxa vara, bowing of the femurs, and flared, irregular metaphyses. What is the most likely diagnosis?

A newborn is diagnosed with an autosomal recessive condition characterized by severe osteopetrosis, recurrent infections, and cranial nerve palsies. The underlying genetic defect most likely disrupts which of the following cellular components?

An 18-month-old girl presents with short stature, severe hypercalcemia, and hypophosphatemia. Radiographs show widespread metaphyseal cupping and fraying with striking osteopenia. Genetic testing reveals a mutation in the PTHR1 gene. What is the diagnosis?

A newborn presents with micromelic severe short stature, rigid equinovarus foot deformities, and bilaterally abducted "hitchhiker" thumbs. Physical examination also reveals cystic swelling of the external ear. What is the underlying genetic defect in this condition?