[Uroporphyrinogen-I-synthetase in erythrocytes in acute intermittent porphyria].

The primary genetic defect in acute intermittent porphyria is a decreased uroporphyrinogen I-synthetase [EC.4.3.1.8] activity. As a beginning of a genealogical study of the known families with members suffering from this disease in the People's Republic of Bulgaria, the red cell uroporphyrinogen I-synthetase was determined in 3 families by the method of Mandel et al [8]. Except for the three propositi, an enzyme deficiency was established in 3 latent carriers of the pathological gene, two of whom had normal values of the urinary epsilon-aminolevulinic acid and porphobilinogen. The determination of red cell uroporphyrinogen I-synthetase proved to be a valuable parameter for revealing the latent AIP.