Suxamethonium sensitivity and segregation of human serum cholinesterase variants at locus, Ch1, among twelve British families.

Sera from 39 individuals with suxamethonium apnoea have been examined. The likelihood of the ChU1ChD1 heterozygotes developing suxamethonium apnoea has been calculated. The results indicate that 1 in 4,000 of normal homozygotes and 1 in 400 of ChU1ChD1 heterozygotes develop suxamethonium apnoea. The period of suxamethonium apnoea in these individuals has been found shorter than that usually seen in ChD1ChD1 homozygotes. An approximate estimate of the frequency of the ChF1 and ChS1 genes has also been calculated. Twelve British families of these suxamethonium apnoea propositi have been examined. The inheritance pattern in all these families was found to be of the Mendelian type. Three of these families have been found to be segregating for the rarer ChF1 gene and two for ChS1 gene, respectively. This present study provides an additional piece of support to the hypothesis that the ChF1 and ChS1 are alleles determining the synthesis of usual and atypical cholinesterase together with the likelihood of ChU1ChD1 heterozygotes having occasional suxamethonium apnoea. In addition, the present report indicates that there may be cholinesterase variants besides dibucaine and fluoride-resistant, 'silent' and C5.