A Brown Tumor of Tibial Diaphysis Masquerading as Malignancy.

A cortical lesion of the tibial diaphysis in a young patient poses a diagnostic challenge to the clinician. Brown tumors, although not very common, may mimic malignancies on radiographs. Brown tumors are destructive lytic lesions of the bone due to increased osteoclastic activity and fibroblastic proliferation in patients with uncontrolled hyperparathyroidism (HPT). They occur after primary or secondary HPT due to renal failure but very rarely due to vitamin D deficiency. We report a rare case of a brown tumor of tibial diaphyses in a young female patient mimicking a locally aggressive tumor with secondary HPT due to a severe vitamin D deficiency. The effect of hyperparathyroidism on bone metabolism is clinically worse in the presence of vitamin D deficiency and, hence, it predisposes patients to brown tumors that can affect any bone in the body. They can be managed conservatively but may require prophylactic fixation in particular cases.