Pseudocholinesterase (soo-doe-koh-lin-ES-tur-ays) deficiency is a rare condition that makes you sensitive to certain muscle relaxants ― succinylcholine or mivacurium ― used during anesthesia. The drugs are designed to briefly relax your muscles during a medical procedure. With pseudocholinesterase deficiency, the body muscles stay relaxed for a longer time. Paralysis of the respiratory muscles causes you to be unable to breathe on your own.

Pseudocholinesterase deficiency can be caused by a genetic defect (mutation) that either is inherited or is acquired due to illness, injury or certain medications.

There is no cure for pseudocholinesterase deficiency. But if you're diagnosed with the condition, your doctor can use other types of muscle relaxants that won't cause prolonged muscle relaxation.

For most people with pseudocholinesterase deficiency, no signs or symptoms of the condition occur until they're exposed to the muscle relaxants succinylcholine or mivacurium. These drugs are used as part of anesthesia. Then signs and symptoms include muscle relaxation or muscle paralysis that lasts for several hours, with the inability to breathe on your own. The length of muscle relaxation may vary widely among people with this deficiency.

When to see a doctor

If you have a family history of pseudocholinesterase deficiency or a family member who had any problem with anesthesia, tell your doctor before you have any medical procedure that requires anesthesia.

If you have pseudocholinesterase deficiency, your body lacks or has a reduced amount of the enzyme needed to break down (metabolize) drugs known as choline esters. These drugs, succinylcholine and mivacurium, are used as part of anesthesia to relax the muscles during medical procedures.

Pseudocholinesterase deficiency causes the muscles to stay relaxed for too long, which prevents you from moving or breathing on your own for a few hours after receiving the drug. How long it takes your body to metabolize the medication depends on how much pseudocholinesterase enzyme is produced and how well it functions.

Pseudocholinesterase deficiency can be inherited or acquired.

Inherited pseudocholinesterase deficiency

Inherited pseudocholinesterase deficiency is caused by a defect in the butyrylcholinesterase (BCHE) gene. This gene provides the instructions to make the pseudocholinesterase enzyme that's needed to break down choline esters. This genetic defect results in a poorly functioning enzyme or lack of enzyme production.

Genetic testing can reveal whether you have this abnormal gene. To have the condition, you must inherit two abnormal genes ― one from each of your parents (autosomal recessive inheritance). If you inherit only one abnormal gene, you won't have the condition. However, you may process choline esters at a slower rate than those without an abnormal gene.

With one abnormal gene, you are a carrier and you can pass the abnormal gene to your children. But they won't develop the condition unless they also inherit an abnormal gene from the other parent.

Acquired pseudocholinesterase deficiency

Pseudocholinesterase deficiency can be acquired as a result of conditions that reduce production of the pseudocholinesterase enzyme, such as chronic infections, kidney or liver disease, malnutrition, severe burns, cancer, or pregnancy. Certain drugs also can reduce production of the enzyme, causing a deficiency.

Your risk of having pseudocholinesterase deficiency is higher if you or a first-degree relative, such as a parent, child or sibling, has:

• An abnormal gene associated with the condition
• A history of an event during anesthesia that is suspected to be pseudocholinesterase deficiency

If you have a family history of pseudocholinesterase deficiency or have a family member who had any problem with anesthesia, tell your doctor before getting a medical procedure that requires general anesthesia. If you have a family history of pseudocholinesterase deficiency, you can prevent problems during anesthesia by getting testing before the procedure.

Evaluating your risk of pseudocholinesterase deficiency allows your anesthesiologist to avoid certain drugs, if needed.

Pseudocholinesterase deficiency may be suspected when you have problems recovering muscle control and breathing after receiving the muscle relaxant succinylcholine or mivacurium as part of anesthesia. A blood test can be done to measure pseudocholinesterase enzyme activity.

To diagnose inherited pseudocholinesterase deficiency, the abnormal gene that causes the condition are identified using genetic testing. A sample of your blood is collected and sent to a lab for analysis. Ask your doctor if family members should be tested before surgery as well.

If you have pseudocholinesterase deficiency, your anesthesiologist can avoid giving you drugs that may trigger prolonged muscle relaxation and choose other muscle relaxants instead.

There is no cure for pseudocholinesterase deficiency. If you have the condition and you receive muscle relaxants that prolong your anesthesia recovery, you'll likely need medical assistance. If needed, mechanical ventilation support and sedation are provided while you recover and start breathing on your own.

With pseudocholinesterase deficiency, you may also be sensitive to other drugs and chemicals. These can include the local anesthetic procaine and certain agricultural pesticides.

If you've been diagnosed with pseudocholinesterase deficiency, wear a medical alert bracelet or necklace. This lets health care professionals know of your risk, especially in an emergency.