Normocholesterolemic dysbetalipoproteinemia with xanthomatosis

A patient is described who has marked palmar xanthomatosis associated with a normal concentration of plasma cholesterol. Analysis of xanthomas revealed them to contain large quantities of cholesterol with both intra- and extracellular lipids. Examination of plasma lipoproteins showed them to be consistent with a pattern of dysbetalipoproteinemia (Type III hyperlipoproteinemia). VLDL had β-mobility on electrophoresis, a high cholesterol/triglyceride ratio, and increased apoprotein B. However, arginine-rich apoprotein was not increased in VLDL, in contrast to hypercholesterolemic patients with the Type III pattern. Nevertheless, the E₃ subfraction of the arginine-rich apoprotein was virtually absent, which is characteristic of dysbetalipoproteinemia. Cholesterol and bile acid synthesis were in the normal range. Thus, of particular interest was the development of severe xanthomatosis without hypercholesterolemia in this patient. Therefore, tissue accumulation of cholesterol was apparently the result of a qualitative abnormality in lipoproteins and not due to an excess of plasma cholesterol.