Pseudocholinesterase (soo-doe-koh-lin-ES-tur-ays) deficiency is a rare disorder that makes you sensitive to certain muscle relaxants — succinylcholine or mivacurium — used during general anesthesia. Mivacurium is no longer available in the United States but is sometimes used in other countries.

Succinylcholine is a drug designed to briefly relax your muscles during a medical procedure, such as surgery. With pseudocholinesterase deficiency, the body muscles stay relaxed for a longer time than expected.

This temporary loss of the ability to move your muscles (paralysis) makes you unable to breathe or move on your own. This can last for several hours. You may need help breathing with a mechanical ventilator until you can start breathing on your own.

Pseudocholinesterase deficiency can be caused by a gene change (mutation) that is inherited. This condition can also be caused by illness, injury or certain medications.

There is no cure for pseudocholinesterase deficiency. But if you're diagnosed with the disorder, your health care provider can use other types of muscle relaxants that won't cause muscle paralysis that lasts longer than expected.

For most people with pseudocholinesterase deficiency, no signs or symptoms of the condition occur until you get the muscle relaxant succinylcholine. This medication is used as part of anesthesia.

Signs and symptoms of pseudocholinesterase deficiency include muscle relaxation or muscle paralysis that lasts several hours longer than expected. During that time, you can't move or breathe on your own. The length of time may vary widely among people with this disorder.

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

If you have pseudocholinesterase deficiency, your body has no pseudocholinesterase or an amount that's too low. This enzyme is needed to break down (metabolize) drugs known as choline esters. Succinylcholine is used as part of anesthesia to relax the muscles during medical procedures.

Pseudocholinesterase deficiency causes the muscles to stay relaxed for too long after getting succinylcholine. This prevents you from moving or breathing on your own for a few hours longer than expected. How long it takes your body to metabolize the drug depends on how much pseudocholinesterase enzyme you produce and how well it functions.

Pseudocholinesterase deficiency can be inherited or acquired.

Inherited pseudocholinesterase deficiency

Inherited pseudocholinesterase deficiency is caused by a change in the butyrylcholinesterase (BCHE) gene. This gene provides the instructions to make the pseudocholinesterase enzyme that's needed to break down choline esters. If you have this changed gene, either you don't produce this enzyme or the enzyme does not work well.

Genetic testing can show whether you have this gene change. To have pseudocholinesterase deficiency, you must inherit two affected genes — one from each of your parents (autosomal recessive inheritance). If you inherit only one affected gene, you won't have the disorder. But you may process choline esters at a slower rate than people who don't have an affected gene.

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

Acquired pseudocholinesterase deficiency

You can develop pseudocholinesterase deficiency as a result of conditions that cause you to make less of the pseudocholinesterase enzyme. These conditions include chronic infections, kidney or liver disease, malnutrition, severe burns, cancer, or pregnancy. Certain medications also can reduce production of the enzyme. Acquired pseudocholinesterase deficiency is not inherited and cannot be passed to your children.

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

• A gene change that causes the disorder
• A history of a problem during anesthesia that is suspected to be caused by pseudocholinesterase deficiency

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

If you have a family history of pseudocholinesterase deficiency, you can prevent problems during anesthesia by having testing before the procedure.

Evaluating your risk of pseudocholinesterase deficiency allows your health care provider to avoid certain muscle relaxants, if needed.

Pseudocholinesterase deficiency may be suspected when you have problems recovering muscle control and breathing after you get the muscle relaxant succinylcholine as part of anesthesia. A blood test can tell if you have enough of the pseudocholinesterase enzyme.

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

If you have pseudocholinesterase deficiency, the health care provider who gives you anesthesia (anesthesiologist) can avoid succinylcholine that may trigger prolonged muscle relaxation. The anesthesiologist can choose other muscle relaxants instead.

There is no cure for pseudocholinesterase deficiency. If you have the disorder and you receive a muscle relaxant that prolongs your anesthesia recovery, you'll likely need medical assistance. If needed, a machine that takes over the work of breathing (mechanical ventilation support) and sedation are provided while you recover and start breathing on your own. This may take several hours.

With pseudocholinesterase deficiency, you may also be sensitive to other medications. These can include local numbing medications, also called local anesthetics. Examples are procaine, tetracaine, benzocaine and cocaine.

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