Hereditary progressive mucinous histiocytosis.

We describe hereditary progressive mucinous histiocytosis, a rare autosomal dominant non-Langerhans cell histiocytosis, in a mother and daughter. Both had similar, progressive eruptions of skin-colored to red-brown papules on the nose, hands, forearms, and thighs. Light microscopy showed small collections of epithelioid histiocytes and telangiectatic vessels in the upper dermis of early lesions. In the mid dermis of early and well-developed lesions, nodular aggregates of tightly packed spindle-shaped cells were seen. Moderate to extensive mucin production was demonstrated in epithelioid histiocytes and spindle-shaped cells. Electron microscopy of spindle-shaped cells revealed many dendritic histiocytes with abundant lysosomal storage organelles such as myelin bodies and zebra bodies. Immunohistochemistry showed expression of macrophage antigens (CD68; MS-1 high-molecular-weight protein) in epithelioid histiocytes and in some of the spindle-shaped cells. The histologic and immunohistochemical features of hereditary progressive mucinous histiocytosis most closely resemble solitary histiocytoma/cellular-type dermatofibroma.