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USMLE Step 1 Questions
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A 5 year old boy’s height is found to be in the lowest 5th percentile for his age. He receives minimal sunlight during the day and he is lactose intolerant. He otherwise has no known health problems and takes no medications/supplements. Which of the following most likely describes X-ray findings of his hips and lower extremities?
Correct Answer: B. Diffuse radiolucency with excess osteoid and bowing
The child has signs of Vitamin D deficiency, or rickets, secondary to inadequate sunlight exposure and poor calcium intake. Vitamin D is necessary to absorb calcium and phosphate from intestinal mucosa. In its absence, bone cannot be mineralized, so there is an excess of osteoid (unmineralized bone) and diffuse osteopenia. Bowing (genu varum) is a deformity of the legs that characterizes rickets. In adults, this condition is called osteomalacia.
Diffuse osteolytic lesions filled with cystic spaces describes osteitis fibrosa cystica, an osteolytic condition secondary to hyperparathyroidism where resorbed bone is replaced by fibrous tissue. Patchy blastic and lytic lesions throughout pelvis and femurs characterizes Paget’s disease, a disorder of deranged bone remodeling that usually affects the elderly. Diffusely increased bone density occurs in Osteopetrosis, which is caused by osteoclast dysfunction leading to susceptibility to fractures from “marble bones.” Without Vitamin D supplementation and adequate calcium intake, growing children have no source of minerals to build bone, and can develop permanent skeletal deformities.
1. QuestionCategory: Pathology
A 5-year-old boy’s height is found to be in the lowest 5th percentile for his age. He receives minimal sunlight during the day and he is lactose intolerant. He otherwise has no known health problems and takes no medications/supplements. Which of the following most likely describes X-ray findings of his hips and lower extremities?Correct