Familial hyperchylomicronaemia in four families. Problems in diagnosis, management, and aetiology reviewed.

We report on the clinical and biochemical findings of 8 patients with familial hyperchylomicronaemia (type I hyperlipoproteinaemia) from 4 separate kindreds. The diagnosis is generally easily established by the presence, in standing plasma, of a creamy chylomicron layer over a clear infranatant and by the large predominance of triglycerides over cholesterol in the plasma. Additional aids are the presence of chylomicrons on lipoprotein electrophoresis and the markedly reduced liberation of lipolytic activity into the plasma of these patients, after the administration of heparin. Difficulties in diagnosis may arise in patients on reduced fat diets, resulting in an increase of very low density lipoproteins and a type IV or V phenotype. The precise nature of the primary genetic defect remains to be established but the disorder appears to be aetiologically distinct from type IV or V hyperlipoproteinaemia. Reduction of chylomicron, and hence of triglyceride values in the plasma, is wholly dietary.