I am going to answer the sample USMLE Step 2 CK Questions with Explanation. These questions are available at USMLE.org
An 18-month-old boy is brought to the emergency department by his mother 30 minutes after he fell from his bed onto the floor. Two months ago, he sustained a fracture of the right humerus when he fell while playing in the park. The fracture healed quickly with immobilization and casting. His mother sustained several bone fractures in early childhood, but she currently does not have any medical concerns. On arrival, the boy is crying. Pulse is 162/min, respirations are 48/min, and blood pressure is 122/80 mm Hg. Examination discloses bluish sclera and ecchymoses and tenderness over the right tibia. X-ray of the right lower extremity confirms a fracture of the tibia. The right lower extremity is immobilized with a cast. Limitation of physical activity is recommended to prevent future fractures.
Given this patient’s condition, it is most appropriate for which of the following types of screening to be done regularly?
(B) DEXA scan
(D) Retinal examination
(E) Serum calcium and vitamin D concentrations
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This patient’s presentation is consistent with osteogenesis imperfecta (OI), a genetic disorder characterized by brittle bones and susceptibility to fractures, often with minimal trauma. Given the family history of multiple fractures in the mother’s early childhood and the presence of bluish sclera, which is a characteristic feature of OI, this diagnosis is highly likely.
OI is associated with an increased risk of various complications, including hearing loss, cardiovascular abnormalities, and ocular problems. Therefore, regular screening is important to detect and manage these complications early.
Hearing loss can occur in some individuals with OI due to abnormalities of the middle ear ossicles or inner ear structures. Therefore, regular Audiography may be warranted as a screening measure in individuals with OI to monitor for hearing impairment.
(B) DEXA scan: Dual-energy X-ray absorptiometry (DEXA) scans are used to measure bone mineral density and are often employed in assessing bone health in conditions like osteoporosis. However, in OI, bone mineral density may not accurately reflect the bone fragility seen in the condition, and DEXA scans are not considered the standard screening tool for OI.
(C) Echocardiography: While cardiovascular abnormalities can occur in OI, they are less common compared to other manifestations such as fractures and hearing loss. Routine echocardiography screening is not typically indicated in OI unless there are specific cardiovascular concerns.
(D) Retinal examination: Ocular problems, particularly retinal detachment, are significant complications of OI but not as frequent as hearing problems. Routine visual examination is recommended if there are visual problems.
(E) Serum calcium and vitamin D concentrations: While monitoring serum calcium and vitamin D levels may be important for overall bone health, routine screening for these parameters is not specific to OI and may not directly address the primary concerns associated with the condition.
The correct answer is (A) Audiography