The clinical, biochemical, and familial presentation of type V hyperlipoproteinemia in childhood.
Primary type V hyperlipoproteinemia was identified in two preadolescent children. The propositus (kindred N) was a 10-year-old girl with severely creamy plasma, lipemia retinalis, hypertriglyceridemia (triglyceridelevel, 6,800 mg/100 ml), and ypercholesterolemia (cholesterol level, 490 mg/100 ml). Her parents and an 8-year-old sister all had endogenous hypertriglyceridemia (type IV hyperlipoproteinemia). In kindred A, an 11-year-old boy had triglyceride levels as high as 1,100 mg/100 ml and recurrent abdominal pain. His father had type V hyperlipoproteinemia; his mother was normal. All three 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 one child with type IV hyperlipoproteinemia. HTL level was normal to above normal in both kindreds. Most patients had a normal H level, but one parent (kindred N) had no preheparin H and very low levels of postheparin H. There was a strong correlation (r = 0.58, significant at less than 1% level) between release of LPL and H but not between HTL and H (r= 0.22). The mean (+/- 1 S.D.) levels of the enzymes were as follows: LPL, 2.8 +/- 0.7 micronmol/ml/hr in kindred N and 5.4 +/- 2.2 micronmol/ml/hr 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 micronmol/ml/hr in kindred N and 14.9 +/- 6.3 micronmol/ml/hr in kindred A. The enzymatic activities of kindreds N and A were significantly different for LPL (P less than .001) and H (.025 less than P less than .05) but not for HTL. All but one child had at least one high insulin level, which was accompanied by hyperglycemia in two children. The hypertriglyceridemia in all but one child was ameliorated on therapeutic diets. These data suggest that the genetic basis of the hypertriglyceridemia in these two families is different and that hyperchylomicronemia in childhood is not confined to the rara type I hyperliporproteinemia.