[Disseminated xanthosiderohistiocytosis with cardiac involvement and monoclonal gammapathy].

Xanthosiderohistiocytosis is a rare non-Langerhans histiocytosis (4 reported cases). The clinical characteristics include diffuse, sometimes deep, dark-brown infiltrations of the skin. Histological examination reveals abundant deposits of haemosiderin within the histiocyte proliferation. This entity is a clinical form of Montgomery's disease (xanthoma disseminatum) which has been reported in over 100 cases. Our case of disseminated xanthosiderohistiocytosis was particular because it involved the heart and was associated with a monoclonal gammapathy. Five cases have been reported associating xanthoma disseminatum and monoclonal gammapathy, including one case of xanthosiderohistiocytosis. In our case, rapidly increasing levels of monoclonal immunoglobulin suggested an evolution towards a myeloma. A monoclonal gammapathy should be looked for and monitored in cases of xanthosiderohistiocytosis, and more generally xanthoma disseminatum because of the risk of developing lymphoma or myeloma.