Fructose-1,6-diphosphatase deficiency: diagnosis using leukocytes and detection of heterozygotes with radiochemical and spectrophotometric methods.

The first two cases of fructose-1,6-diphosphatase (FDPase) deficiency from the Middle East have been diagnosed on leukocytes using a spectrophotometric assay and a new radiochemical technique. The control mean for FDPase measured by the spectrophotometric assay was 178.2 nm mg-1 h-1 (n = 12), 66.8 nm mg-1 h-1 for obligate heterozygotes (n = 4) and non-detectable in the two patients. By the radiochemical assay the values were controls, 103.3; heterozygotes, 20.6; patients, 0.46 and 3.5 nm mg-1 h-1. Using both methods it was possible to identify two certain FDPase heterozygotes and three non-carriers in the family of one of the probands. The radiochemical method was found to be more effective in differentiating heterozygotes from controls than the spectrophotometric method. However, either technique may be conveniently used for the diagnosis of FDPase deficiency in leukocytes.