Xanthomatosis is a disease of lipoid metabolism in which storage tumors of lipoid appear in various places and in various organs, sometimes profoundly affecting the bodily health and welfare. There are five clinical entities included under this heading; namely, Gaucher's disease, Niemann-Pick's disease, Schüller-Christian's disease, the xanthomas occurring in icterus, diabetes and pregnancy, and the so-called essential xanthomatosis. The first type, Gaucher's disease, involves chiefly the spleen, occurs at any age but most frequently in female children, is familial, and is fairly benign. Niemann-Pick's disease is appropriately called hepatosplenomegaly because of the marked enlargement of the liver and spleen, is racial rather than familial, occurring almost entirely in infants of the Jewish race, and is rapidly fatal. Schüller-Christian's disease occurs chiefly in young children, is characterized by involvement of the bones of the skull, occasionally other bones, with frequent association of diabetes insipidus, exophthalmos and gingivitis, less commonly dwarfism, adiposogenital