Pseudohomozygous type II hyperlipoproteinemia.

Nodular xanthomas on both elbows and a streak-like xanthoma on the intergluteal area developed in a 4-year-old girl with type IIa hyperlipoproteinemia. She had no disease associated with secondary hypercholesterolemia and no family history of hypercholesterolemia. Her xanthomas regressed under fat restriction diet and cholestyramine therapy. She was diagnosed as having pseudohomozygous type II hyperlipoproteinemia. The low-density lipoprotein (LDL) receptor activities of her cultured fibroblasts in terms of binding, internalization and degradation rate of LDL were normal. These results are consistent with a new syndrome of pseudohomozygous type II hyperlipoproteinemia and suggest that the mechanism of hypercholesterolemia, which induced xanthoma, differs from familial hypercholesterolemia.