Butyrylcholinesterase (BCHE) - Deficiency and Post-operative Apnoea [T88.7]
OMIM number: 177400 (BCHE)
Dipl.-Biol. Birgit Busse
Postoperative apnoea is a severe complication associated with administration of depolarizing muscle relaxants (e.g. suxamethonium, mivacurium), which are metabolized by the enzyme BCHE. Other substrates of BCHE are procaine, tetracaine, cocaine and heroin. Various mutations in the BCHE gene can lead to a reduced enzyme activity and thus to a prolonged metabolism.
The BCHE deficiency is inherited autosomal recessively. If the deficiency remains undetected, acute, life-threatening situations may occur during as well as after anesthesia. With a reduction in enzyme activity to approximately 30% of the standard, the A variant (atypical variant, p.D70G) is associated with severe complications during anesthesia. The K variant (p.A539T) is associated with only a moderate reduction in enzyme activity to approximately 70% of the standard and is usually not associated with a prolonged response to succinylcholine. However, in combination with other factors (pregnancy, anticholinesterase medication, pre-existing conditions) the K variant may become clinically relevant. The allele frequency of the A variant is approximately 2% among all Caucasians, (homozygous frequency 1:3,500), the K variant approximately 12% (homozygous frequency 1:100). For the analysis of the BCHE gene a stepwise diagnostic procedure can be requested. In step I the K and A variant are being detected. In step II the whole BCHE gene is tested for mutations to rule out rare mutations.