Question 99

Question:

A 67 year-old man is evaluated after being treated for a broken arm. He sustained a small hairline fracture of the distal ulna after hitting his arm on a railing. He says it was only a minor bump and is surprised it caused a fracture. Serum chemistry is remarkable for elevated calcium at 11.6, low phosphate at 2.1, and slightly elevated alkaline phosphatase at 98. What is the most likely diagnosis?

Correct Answer: A.  Hyperparathyroidism

Elevated calcium, low phosphate, and elevated alkaline phosphatase are consistent with hyperparathyroidism, which can cause osteopenia, making this patient more susceptible to fracture after trauma. Paget’s disease of bone would be expected to have a markedly elevated alkaline phosphatase (a byproduct of osteoblast activity). In vitamin D deficiency, low serum calcium would be seen. Renal insufficiency would lead to low serum calcium and elevated phosphate. Osteoporosis would not lead to electrolyte abnormalities.