[A rare case of silent cholinesterase genetic variant (author's transl)].

Some patients present prolonged apnea following the administration of succinylcholine because of substantial portion of plasma cholinesterase (the enzyme responsible for the hydrolysis of this muscle relaxant) is present as an atypical variant. Up to the present four types of cholinesterase genes are known which combination can cause apnea to a greater or less extent. Silent homozygous EsEs present apnea of greatest duration due to the complete absence of cholinesterase activity. The case reported belongs to a family of four members and is an example of this extremely uncommon genetic variant, with a frequency of 1/170.000. To determine total cholinesterase activity genetic typing of the whole family was carried out utilizing the spectrophotometric technique of Szasz and Knedel with butirylthiocholine iodide as substrate. Inhibition studies were performed using benzoylcholine and dibucaine, sodium fluoride, scholine, and sodium chloride as inhibitors.