There has been few report concerning clinical features of type III hyperlipoproteinemia (type 3-HL) genetically defined as apolipoprotein E2/2 phenotype not only in Japan but also in the Western countries. We investigated nine type 3-HL cases with E2/2 phenotype (7 males and 2 females). Age was ranged from 41 to 60 years. Serum cholesterol levels were 435±112mg/dl (mean±SD), triglyceride levels were 583±313mg/dl, and HDL-cholesterol levels were 42±9mg/dl. Lipoprotein analysis using PAG-disc electropholesis disclosed increased chylomicron and VLDL fractions in some case. Preparative ultracentrifugation revealed that contents of all lipids in VLDL and IDL fractions were increased. LDL-cholesterol and LDL-phospholipid were decreased but LDL-triglyceride was increased. HDL2-cholesterol levels were decreased but HDL2-triglyceride levels were increased. Twenty-two percent patients (2/9) had xanthoma including tendinous and tuberous one, but classic “xanthoma striata palmaris” was not found. Twenty-two percent patients (2/9) had clinical events of atherosclerotic disease. One had angina pectoris, and another had atherosclerosis obliterans and renal hypertension due to atherosclerotic narrowing of renal arteries.
Thus, the frequency of atherosclerosis in the patients with type 3-HL in Japan seems to be lower than in the Western countries. The reason for this difference remains unclear. We propose the following reasons for it. First, the difference in dietary custom between Japanese and Western people may account for this difference. Japanese take much less fat than Western people in general. Therefore chylomicron-remnant, which is thought to be more atherogenic than VLDL-remnant, might less accumulate in Japanese patients with type 3-HL than in those in the Western countries. The second, the difference in the principal hyperlipoproteinemic gene which accompanied with E2/2 gene to express type 3-HL phenotype might also account for the difference in frequency of atherosclerosis. By the family studies, type IV hyperlipoproteinemia may combine with E2/2 gene in the subjects in this study, while familial combined hyperlipidemia has been thought to be major hyperlipoproteinemia which accompanied with E2/2 gene in type 3-HL in the Western countries.
