C-II anapolipoproteinemia and severe hypertriglyceridemia. Report of a rare case with absence of C-II apolipoprotein isoforms and review of the literature.
A new case of C-II anapolipoproteinemia (complete apolipoprotein C-II deficiency) as the cause of severe hypertriglyceridemia with chylomicronemia (type I lipoprotein phenotype) is described. The patient was a five-year-old boy living in Connecticut. He had splenomegaly, episodic abdominal pain, and bloody stools. Absence of apolipoprotein C-II (and its isoforms C-II1 and C-II2) was documented by a sensitive and specific radioimmunoassay, analytical isoelectric focusing, and in vitro lipolytic assay. Decreased levels of high- and low-density lipoprotein cholesterol and apolipoproteins A-I and A-II and increased levels of plasma triglycerides and apolipoprotein E were found. Post-heparin extra-hepatic lipoprotein lipase activity was within normal range. Incorporation of exogenous purified human apolipoprotein C-II to an incubation mixture of purified lipoprotein lipase and the patient's triglyceride-rich lipoproteins resulted in a dramatic increase in the catabolic rate of the defective triglyceride-rich lipoproteins. The absence of the isoforms of apolipoprotein C-II in this patient indicates that a common gene exists for the C-II isoproteins, which appear to be necessary for normal triglyceride transport in humans. A literature review of 23 reported cases indicates that xanthomas and hepatosplenomegaly are less common in C-II anapolipoproteinemia than in lipoprotein lipase deficiency, the other major etiologic cause of genetic chylomicronemia.
D000293:Adolescent; D000328:Adult; D053304:Apolipoprotein C-II; D001053:Apolipoproteins / Q000097:blood / Q000172:deficiency* / Q000235:genetics; D001056:Apolipoproteins C; D002675:Child, Preschool; D002784:Cholesterol / Q000097:blood; D005260:Female; D006493:Heparin; D006720:Homozygote; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood* / Q000201:enzymology; D007700:Kinetics; D008066:Lipolysis; D008071:Lipoprotein Lipase / Q000172:deficiency; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000097:blood*
D053304:Apolipoprotein C-II; D001053:Apolipoproteins; D001056:Apolipoproteins C; D014280:Triglycerides; D006493:Heparin; D002784:Cholesterol; D008071:Lipoprotein Lipase