Hereditary butyrylcholinesterase deficiency

Hereditary butyrylcholinesterase (BChE) deficiency, also known as pseudocholinesterase deficiency or serum cholinesterase deficiency, is a genetic condition characterized by reduced or absent activity of the enzyme butyrylcholinesterase (also called plasma cholinesterase or pseudocholinesterase). This enzyme is responsible for metabolizing certain drugs, most notably the muscle relaxants succinylcholine (suxamethonium) and mivacurium, which are commonly used during general anesthesia. Individuals with this deficiency are typically asymptomatic under normal circumstances and may be entirely unaware of their condition until they are exposed to these specific medications. When affected individuals receive succinylcholine or mivacurium during surgical procedures, they experience prolonged neuromuscular blockade, which manifests as extended muscle paralysis and prolonged apnea (inability to breathe independently). Instead of the expected 5–10 minutes of muscle relaxation, paralysis can last from 30 minutes to several hours, requiring prolonged mechanical ventilation until the drug is eventually cleared from the body. This can be a life-threatening situation if not recognized and managed appropriately. The condition primarily affects the neuromuscular system in the context of drug exposure. The condition is caused by variants in the BCHE gene located on chromosome 3q26.1-q26.2. Several variant alleles have been identified, including the atypical (A), fluoride-resistant (F), silent (S), and quantitative (K) variants. Diagnosis is established through measurement of serum cholinesterase activity and inhibition studies (dibucaine number and fluoride number), and can be confirmed by molecular genetic testing. There is no specific treatment for the underlying enzyme deficiency itself. Management focuses on avoidance of triggering drugs, use of alternative non-depolarizing muscle relaxants during anesthesia, and supportive care with mechanical ventilation if prolonged apnea occurs. Genetic counseling and alerting family members are important preventive measures, and affected individuals should carry medical alert identification.

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