Pseudocholinesterase deficiency is an uncommon genetic disorder that makes an affected person very sensitive to any of several anesthetic agents, especially those derived from the drug known as choline. When anesthetic drugs such as succinylcholine or mivacurium are administered to a susceptible person, the muscles that work the lungs may become paralyzed. Mechanical ventilation is essential until the excess anesthetic agent is metabolized and normal breathing is resumed.
Individuals with pseudocholinesterase deficiency have a shortage or absence of the enzyme pseudocholinesterase in their blood serum. If the drug succinylcholine (or another anesthetic derivative of choline) is given during surgery, the respiratory muscles become paralyzed and the patient stops breathing (apnea). Artificial respiration (mechanical ventilation) may be necessary until the drug is eliminated from the body and the affected individual is able to resume breathing. If the person with pseudocholinesterase deficiency is not exposed to a choline-derived anesthetic, he or she may never be aware of having a deficiency of the enzyme pseudocholinesterase.
Pseudocholinesterase deficiency is inherited as an autosomal recessive trait. The faulty gene is located on chromosome 3 (3q26.1-q26.2).
Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome, and females have two X chromosomes. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, 3q26.1-q26.2 refers to a region between bands 26.1 and 26.2 on the long arm of chromosome 3. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.
All individuals carry a few abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.
Pseudocholinesterase deficiency is present at birth and occurs in approximately 1 out of every 1,500 to 2,500 people in the United States. Among Caucasian Americans, it seems to affect males almost twice as often as females.
Diagnosis and Treatment
Testing can be done to determine the presence of pseudocholinesterase deficiency before surgery is performed. If the patient stops breathing for a prolonged period of time during surgery, artificial respiration (mechanical ventilation) can be administered until the patient is able to resume normal breathing.
People with pseudocholinesterase deficiency should warn their relatives to be tested before surgery since this is a genetic disorder. People who have relatives who have died for unknown reasons during surgery should be screened for pseudocholinesterase deficiency prior to undergoing surgery.
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FROM THE INTERNET
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