The silent gene for serum pseudocholinesterase.

The investigations of human serum pseudocholinestrase (acylcholine acylhydrolase) (International Union of Biochemistry, . i96i: 3.I.I.8) suggest the existence of four allelic genes controlling the formation of different enzyme types: gene Elu for usual esterase, Ela for atypical (dibucaine resistant) esterase, El' for a fluoride-resistant type, and Els for a 'silent' gene. The four genes result in the existence of I0 different genotypes (Harris, I964). Until now 7 cases (in 6 families) of complete pseudocholinesterase deficiency, compatible with the homozygous genotype ElsEls,have been described (Liddell, Lehmann, and Silk, I962; Doenicke, Girtner, Kreutzberg, Remes, Spiess, and Steinbereithner, I963; Hodgkin, Giblett, Levine, Bauer, and Motulsky, I965; Goedde, Fuss, Ritter, and Baitsch, i965a; Dietz, Lubrano, and Rubinstein, I965). During a survey on the frequency of atypical pseudocholinesterase in various population groups in Israel, a new case of complete absence of the enzyme was detected by us. Family examinations demonstrated a similar absence of enzyme activity in the serum of two children of the propositus (Fig.). The present report describes the detailed findings in the affected family.