In a total of 13 obligate heterozygotes, Brunzell found considerable phenotypic variation: (1) more than half of heterozygotes had normal TG levels, a few had mild hypertriglyceridemia, while two heterozygotes each had a TG reading >7 mmol/L on at least one occasion; and (2) LPL activity was widely variable, and in one individual was actually higher than in normal controls. Here, LPL is linked to hypertriglyceridemia.