Slient cholinesterase gene in an East Indian family in Trinidad - abstract

ABSTRACT

During a study to determine the frequency distribution of the enzyme pseudocholinesterase (Cholinesterase) in the population of Trinidad, an East Indian individual developed prolonged respiratory apnoea on administration of a routine dose of suxamethonium. This paper reports the results of analyses of the frequency distribution of pseudocholinesterase in the sera from the index case and 19 family members. Cholinesterase was detected qualitatively in the serum, using the Dibucaine Number (DN) and Fluoride Number (FN) tests (normal values 78.8 per cent and 61.4 per cent, respectively), and quantitatively, using the modified Ellman method (normal plasma levels 844 ñ 1.78 u/ml). Patients with low activity of the enzyme (inhibited < 20 per cent by dibucaine) are "suxamethonium-sensitive". DN and FN values in the serum of the index case could not be determined because of the negligible enzyme activity (0.17 u/ml). Of the 6 of 7 siblings available for testing, 1 was found with undeterminable DN and FN values and even lower enzyme activity (0.09 u/ml). The proband's marital partner, 2 children and father had normal enzyme patterns. This condition of `trace' enzyme activity is controlled by a `silent gene' (AU)