Detection of heterozygotes for fructose 1,6-diphosphatase deficiency by measuring fructose 1,6-diphosphatase activity in their cultured peripheral lymphocytes.

The fructose 1,6-diphosphatase activities in peripheral lymphocytes from the parents of a patient with fructose 1,6-diphosphatase deficiency were lower than the mean value of normal controls, but the value of the mother overlapped lower values for normal controls. The fructose 1,6-diphosphatase activities in lymphocytes of normal adults and the parents increased progressively during in vitro culture, but no enzyme activity could be detected in the lymphocytes of the patient even after culture. None of the values for the parents overlapped those of normal controls on either day 5 or 10 of culture. Thus, it seems probable that heterozygotes for fructose 1,6-diphosphatase deficiency can be distinguished from normal individuals by measuring the fructose 1,6-diphosphatase activity in their cultured lymphocytes.