Pathologic fracture in systemic mastocytosis. Radiographic spectrum and review of the literature.

Systemic mastocytosis is a multiorgan disease that most commonly affects the skin and skeletal system. Radiographically, the skeletal changes in the majority of patients consist of either a wide-spread mixture of bone lysis and osteosclerosis or generalized osteoporosis. The osteoporotic form is less well known but may lead to severe generalized demineralization and pathologic fractures. Mast cells secrete a number of substances, two of which (heparin and prostaglandins) are believed to have a role in the induction of osteoporosis. Sclerotic lesions are induced by another mast cell by-product, histamine. One hundred seventy-eight cases of bony mastocytosis have been reported in the literature, including the four patients in the present report. Special staining procedures are necessary for identification of mast cells. Diagnosis may be delayed in patients who do not have the skin lesions (urticaria pigmentosa) and in the osteoporotic form of the disease.