Plane xanthomata associated with multiple myeloma and hyperlipoproteinaemia.

A case of plane xanthomatosis associated with multiple myeloma and hyperlipoproteinaemia in a 62-year-old woman is reported. The patient had IgG type lambda paraproteinaemia and type II A hyperlipoproteinaemia. The IgG paraprotein showed binding activity against high-density lipoprotein. It could not be demonstrated that these paraprotein-lipoprotein complexes were responsible for the hyperlipidaemia. Microchemical analysis of pathological skin demonstrated a high content of triglycerides, similar to that in eruptive xanthomata. No correlation was found between the lipid composition of the xanthomatous skin and the serum lipid composition. The results obtained with an in vitro culture method showed that the paraprotein present in the patient's serum was synthesized in the bone marrow but not in the normal or pathological skin.