Mastocytosis

Mastocytosis is a generic term referring to a spectrum of rare disorders characterized by the proliferation of mast cells in tissues. Mastocytosis in the bone is a very rare, systemic disease usually limited to adults. Osseous changes are the most constant abnormality in systemic mastocytosis. Lesions involve both the axial and appendicular skeleton and may be diffuse or focal. Rarely, patients with osseous disease lack cutaneous involvement. Patients may present weight loss, weakness, and hematologic abnormalities due to replacement of the bone marrow. Bone lesions are usually asymptomatic but may present bone pain. Both radiolytic and radiodense lesions occur. Radiolytic changes may be focal or diffuse. Histologically, there is focal or diffuse infi ltration by mast cells, admixed with other marrow elements, including eosinophils and fi broblasts, or in solid sheets. Immunostain for mast cell tryptase is positive. Patients with “bone-only” disease follow an indolent course. Treatment is supportive and is geared to reducing systemic symptoms.