The Clinical, Biochemical, and Familial Presentation of Type V Hyperlipoproteinemia in Childhood

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Abstract
Primary type V hyperlipoproteinemia was identified in 2 preadolescent children. The propositus (kindred N) was a 10 yr old girl with severely creamy plasma, lipemia retinalis, hypertriglyceridemia (triglyceride level, 6800 mg/100 ml) and hypercholesterolemia (cholesterol level, 490 mg/100 ml). Her parents and an 8 yr old sister all had endogenous hypertriglyceridemia (type IV hyperlipoproteinemia). In kindred A, an 11 yr old boy had triglyceride levels as high as 1100 mg/100 ml and recurrent abdominal pain. His father had type V hyperlipoproteinemia; his mother was normal. All 3 of his older teenage siblings had type IV hyperlipoproteinemia. The enzymatic activities of lipoprotein lipase (LPL), hepatic triglyceride lipase (HTL) and histaminase (H) were studied in postheparin plasma. The LPL level was low in the children and both parents in kindred N. LPL level in kindred A was normal, except for 1 child with type IV hyperlipoproteinemia. HTL level was normal to above normal in both kindreds. Most patients had a normal H level, but 1 parent (kindred N) had no preheparin H and very low levels of postheparin H. There was a strong correlation (r [correlation coefficient] = 0.58, P < 1%) between the release of LPL and H but not between HTL and H (r = 0.22). The mean (.+-. 1 SD) levels of the enzymes were as follows: LPL, 2.8 .+-. 0.7 .mu.mol/ml per h in kindred N and 5.4 .+-. 2.2 .mu.mol/ml per h in kindred A; H, 13.4 .+-. 6.8 units/ml in kindred N and 22.0 .+-. 11.9 units/ml in kindred A; and HTL, 18.0 .+-. 7.1 .mu.mol/ml per h in kindred N and 14.9 .+-. 6.3 .mu.mol/ml per h in kindred A. The enzymatic activities of kindreds N and A were significantly different for LPL (P < .001) and H (.025 < P < .05) but not for HTL. All but 1 child had at least 1 high insulin level, which was accompanied by hyperglycemia in 2 children. The hypertriglyceridemia in all but 1 child was ameliorated on therapeutic diets. The genetic basis of the hypertriglyceridemia in these 2 families may be different. Hyperchylomicronemia in childhood is probably not confined to the rare type I hyperlipoproteinemia.