Lecithin-cholesterol acyltransferase (LCAT) deficiency was first described in a Norwegian family as an inborn error of metabolism. Altogether, 35 patients in 18 families have been identified. The authors report the first German patient, who presented with the characteristic clinical features of corneal opacity, proteinuria, and mild anemia. Renal biopsy revealed foam cells and an increased mesangial matrix in the glomeruli. Confirmation of the clinical diagnosis of LCAT deficiency was obtained by plasma enzyme and lipid analyses. Functional LCAT activity was not detected in incubated plasma by chemical or radiochemical methods, although rocket immunoelectrophoresis indicated that the patient had about one-third of normal LCAT mass. In keeping with other reports of LCAT deficiency, apoE-rich discoidal particles were seen in the patient's high-density lipoprotein fraction by electron microscopic examination.