Pseudocholinesterase deficiency is characterised by insufficiently low levels of pseudocholinesterase. Pseudocholinesterase is a plasma enzyme that metabolises choline esters, such as the muscle relaxants succinylcholine and mivacurium [1]. The aetiology of pseudocholinesterase deficiency can be genetic (hereditary) or acquired. Patients typically present with prolonged post-operative apnoea and paralysis following administration of either succinylcholine or mivacurium during the induction of general anaesthesia. 

Hereditary pseudocholinesterase deficiency (ICD-10 E88.0) is an autosomal recessive condition caused by atypical variants of the butyrylcholinesterase (BChE) gene located on chromosome 3 (3q26.1-q26.2). The prevalence of homozygosity is estimated at 1:3,000, while heterozygosity has an estimated prevalence of 1:25 [2, 3]. Interestingly, the prevalence of pseudocholinesterase deficiency seems to be much higher in certain ethnic groups, such as individuals of Turkish or Egyptian descent [1, 4], the Vysya community in India [5], or a number of Alaskan Native communities [6]. 

Heterozygosity may also be associated with a slightly prolonged duration of action of succinylcholine and mivacurium. 

Acquired forms of the condition may be caused by pregnancy, liver disease, and malnutrition, amongst others [2]. Furthermore, other potential causes of reduced pseudocholinesterase levels include malignancy [7], renal disease [8], and burns [9]. Additionally, a number of drugs may inhibit pseudocholinesterase activity [e.g., 10]. 

Acquired causes of the deficiency seldom result in clinically noticeable symptoms. This is because enzyme activity usually does not fall below 50%, i.e. the estimated threshold of clinical relevance [11]. Nevertheless, a combination of genetic and acquired causes (such as pregnancy and heterozygosity) could cumulatively result in a clinically relevant reduction of enzyme activity, thus causing clinical symptoms [2, 11, 12]. 

A routine preoperative work-up will not usually identify pseudocholinesterase deficiency unless a patient’s medical or family history is remarkable in this regard. Diagnoses are typically made once a patient fails to adequately recover from paralysis following an administration of succinylcholine or mivacurium. Laboratory tests such as enzyme activity assays and the so-called dibucaine test confirm the diagnosis. A genetic analysis of the patient (and respective relatives) can help establish the aetiology of the condition. 

Pseudocholinesterase deficiency has an excellent prognosis. However, a causal treatment of the condition does not currently exist. Instead, typical treatment is supportive, consisting of prolonged mechanical ventilation, sedation, and the monitoring of neuromuscular function until the patient can be safely extubated.