Further observations on familial hypobetaliproteinaemia.

A family with hypobetalipoproteinaemia with 10 affected members is described. In six patients low density lipoprotein cholesterol (LDL-c) concentrations were about 10 % of normal. In four LDL-c was reduced to about 50 % of normal; these four patients probably represent the "intermediate" form of hypobetalipoproteinaemia. This variation in total cholesterol concentration and LDL-c among the affected individuals of the same family could reflect differences of expression in a single aberrant gene or additive expression of a gene at a second locus.