Case report: pathologic long bone fracture in a patient with systemic mastocytosis.

Systemic mastocytosis is characterized by clonal proliferation of mast cells, which cause disease by accumulating in various organs and releasing their chemical products into tissues. We highlight a patient with systemic mastocytosis that caused a pathologic femur fracture in a 63-year-old man with minimal trauma. The typical presentation of bone involvement is a combination of mixed sclerotic and osteolytic lesions, but this patient also had osteopenia. Although bone involvement is common in patients with systemic mastocytosis, pathologic fractures outside the vertebral column are rare. The patient was treated with intramedullary fixation of his femur and retained adequate fixation at the time of his death 7 months postoperatively. We review the literature on pathologic fractures outside the vertebral column in patients with systemic mastocytosis.