Pseudocholinesterase deficiency is an uncommon inherited condition affecting how the body processes certain drugs. This condition is not a disease and does not manifest with any health issues in a person’s daily life. The deficiency becomes apparent only when specific medications are administered, often during medical procedures.
The Role of Pseudocholinesterase and Anesthesia
The pseudocholinesterase enzyme, also known as butyrylcholinesterase, breaks down chemical messengers called choline esters, including the neurotransmitter acetylcholine. In a clinical setting, its primary role is metabolizing certain drugs used for general anesthesia. The enzyme rapidly breaks down these drugs, allowing their effects to wear off predictably.
This function is apparent during anesthesia when muscle relaxants like succinylcholine and mivacurium are used. These medications are administered to relax the muscles, which helps surgeons and aids in inserting a breathing tube. In individuals with normal enzyme function, the effects of these drugs last only a few minutes.
In a person with this deficiency, the enzyme does not function correctly. When drugs like succinylcholine or mivacurium are given, they are not metabolized at the expected rate. This leads to a prolonged period of muscle paralysis that can last for hours after surgery. This paralysis affects all muscles, including the diaphragm, preventing the person from breathing on their own in a state known as apnea.
Prolonged paralysis following an anesthetic procedure is frequently the first indication of the deficiency. Anesthesiologists expect a rapid recovery, so when a patient fails to resume breathing and movement on their own long after surgery, it signals an issue with drug metabolism. The patient must be supported by a mechanical ventilator until the anesthetic drug wears off and muscle function returns.
Genetic and Acquired Causes
The most common cause of pseudocholinesterase deficiency is genetic, resulting from a mutation in the butyrylcholinesterase (BCHE) gene. This gene provides instructions for the liver to produce the enzyme. Variations in the BCHE gene lead to an enzyme that is less effective or produced in smaller amounts.
This condition is inherited in an autosomal recessive pattern, meaning an individual must inherit two copies of the altered BCHE gene—one from each parent. A person who inherits only one copy is a carrier. Carriers may produce a reduced amount of the enzyme but often not low enough to cause significant problems during anesthesia.
While most cases are inherited, it is also possible to have an acquired form of the deficiency. This means a person was not born with the genetic trait but developed low enzyme levels due to other factors. These can include chronic infections, kidney or liver disease, malnutrition, or severe burns. Pregnancy can also temporarily lower enzyme levels, and certain medications can interfere with its production.
Diagnosis and Testing
Pseudocholinesterase deficiency is most often identified after an adverse reaction to anesthesia. If a person or close blood relative has a history of prolonged paralysis after surgery, testing may be recommended. Testing can also be done before a scheduled surgery for those with a known family history, allowing anesthesiologists to prevent a reaction.
The primary diagnostic method is a blood test measuring the activity level of the pseudocholinesterase enzyme in the plasma. Low levels of activity suggest a deficiency. This test confirms the clinical suspicion raised by a patient’s reaction to anesthesia.
To distinguish between genetic and acquired causes, a “dibucaine number” test is used. Dibucaine is a chemical that inhibits the normal enzyme but has less effect on the atypical forms associated with the genetic deficiency. A low dibucaine number indicates an atypical enzyme and confirms an inherited deficiency, while a normal number with low enzyme activity points to an acquired cause.
Management and Patient Precautions
There is no cure for pseudocholinesterase deficiency, so management centers on preventing a reaction by avoiding the drugs that trigger it. Individuals diagnosed with the condition must not be given the muscle relaxants succinylcholine or mivacurium during any medical procedure.
A person with this deficiency can still undergo surgery safely. Anesthesiologists have many alternative anesthetic agents and muscle relaxants, such as rocuronium, that are metabolized through different pathways. The medical team must be aware of the condition ahead of time to plan accordingly.
Individuals with a confirmed diagnosis must communicate this information to all of their healthcare providers, including surgeons, anesthesiologists, dentists, and emergency medical personnel. Clear communication is the most effective way to prevent an adverse event.
For emergencies, patients are advised to wear a medical alert bracelet or carry a card to warn healthcare workers about the deficiency. Informing family members is also important, as they can advocate for the patient and because the condition can be inherited.