Plane xanthoma and multiple myeloma with lipoprotein--paraprotein complexing.

Clinicopathologic findings are reported of a woman with generalized plane xanthoma, multiple myeloma (IgG type K), and hyperlipemia with very high levels of serum cholesterol and triglyceride. Complexing of the serum lipoproteins and immunoglobulins had cryoglobulin properties and was separable by ultracentrifugation. Immunofluorescent studies of skin and bone marrow demonstrated deposits of IgG with low density lipoprotein apoprotein and IgG with beta-lipoprotein, respectively. Although immunosuppressive therapy resulted in return of serum IgG, lipid, and lipoprotein levels to normal, the patient died from the myeloma. Serum lipoprotein-paraprotein complexes have been demonstrated in at least 20 other cases of cutaneous xanthomatosis and myeloma. This interaction may result in an autoimmune hyperlipemia.