By L. Ronar. California State University, Northridge.
The authors family member who has MH susceptibility should tell explained that although MH susceptibility has typically their doctor about their family history buy tadalafil 10mg without a prescription impotence drugs for men. Since MH may go been described as an autosomal dominant trait caused by unrecognized cheap 20mg tadalafil fast delivery erectile dysfunction treatment online, it is important that anyone who has had a a single gene that is passed from one generation to the close relative die from anesthesia notify the anesthesiol- next, they believe MH susceptibility may actually depend ogist before any type of surgery is planned. People with upon various genetic changes that occur in more than one a family history of MH susceptibility may choose to meet gene. RYR1 and DHPR affected person may consider having a test to see if they alpha 1 subunit), not all changes in these genes lead also inherited MH susceptibility. For example, although Although there are many people who have the same at least 20 different genetic changes have been identified symptoms of MH when exposed to trigger drugs, genetic in the RYR1 gene that can lead to MH susceptibility, research has shown that there are probably many genes, some people who have certain types of these changes located on different chromosomes, that can all lead to actually have a different genetic condition that affects the MH susceptibility. This indicates that there is genetic het- muscles called central core disease (CCD). Infants with erogeneity among different families with MH suscepti- this autosomal dominant condition typically have very bility, meaning that different genes can lead to the same poor muscle tone (i. Among families who 2001, researchers identified six different types of MH have CCD, there are some individuals who do not have susceptibility. Although specific genes have been discov- the typical muscle changes, but have MH susceptibility ered for some of these types, others have been linked instead. Hopefully, future research will help scientists only to specific chromosomal regions. The exact number of individuals who are born with a genetic change that causes MH susceptibility is not • MHS3—Located on chromosome 7q21-22. However, it is estimated that internationally one in • MHS4—Located on chromosome 3q13. Specific 50,000 people who are exposed to anesthesia develop an gene and protein unknown. Symptoms such as rapid breath- Signs and symptoms ing, rapid heart rate, and high body temperature can usu- ally be detected with various machines or devices that Although the specific symptoms of malignant hyper- examine basic body functions during surgery. Muscle thermia can vary, the most common findings include: stiffness of the jaw, arms, legs, stomach and chest may be • stiffness/spasms of jaw muscles and other muscles noticed as well. If the diagnosis is made • rapid breathing, causing decreased oxygen and during or after surgery, immediate treatment is needed to increased carbon dioxide in the blood prevent damage to various parts of the body or death. If a • rapid or irregular heartbeat person has a suspicious reaction to anesthesia, he or she • high body temperature (over 110°F) may undergo a muscle biopsy to confirm MH suscepti- bility at a later date. As of March 2001, existing genetic testing identifies some The diagnosis of MH susceptibility can be made changes that have been seen among families with MHS1 before or during a reaction to a triggering drug. Research studies may provide information the diagnosis is made before a susceptible individual is for families with MHS2, MHS3, MHS4, and MHS5 as exposed and/or develops a reaction. Sometimes the testing requires DNA from only one people who learn they have an increased chance for MH affected person, but in other cases, many samples are because they have a relative with MH susceptibility. However, until Testing these individuals requires a surgical procedure genetic technology improves, the contracture test that is called a muscle biopsy, in which a piece of muscle tis- done on muscle tissue will likely remain the “gold stan- sue is removed from the body (usually from the thigh). The muscle is taken to a laboratory and is Treatment and management exposed to halothane (a triggering anesthetic) and caf- feine, both of which cause any muscle tissue to contract, The early identification of an MH episode allows for or tighten. Thus the test is called the caffeine halothane immediate treatment with an “antidote” called dantrolene contracture test (CHCT). This medication prevents the release of calcium viduals with MH susceptibility is more sensitive to caf- from the sarcoplasmic reticulum, which decreases mus- feine and halothane, causing it to contract more strongly cle stiffness and energy production in the cells. In addition, the anesthesiologist will change the whether a person has MH susceptibility or not. However, the test does require surgery, time to recover Immediate treatment is necessary to prevent serious ill- (typically three days), and it is expensive (approxi- ness and/or death. In the United States, many insurance Once a person with definite or suspected MH suscep- companies will pay for the testing if it is needed. The important first step in this process is for peo- learn from their family histories that they have an ple with known or suspected MH susceptibility to talk increased risk for MH before they are exposed to a trig- with their doctors before any surgery, so that only non- ger drug. People with definite or sus- ceptibility is often made during surgery by the pected MH susceptibility should always carry some form anesthesiologist (a physician specializing in anesthesia) of medical identification that describes their diagnosis in GALE ENCYCLOPEDIA OF GENETIC DISORDERS 703 case emergency surgery is needed. The Malignant WEBSITES Hyperthermia Association of the United States provides Larach, Marilyn Green, MD, FAAP. When the antidote (dantrolene sodium) became available in 1979, the sur- vival rate increased to 70–80%. However, 5–10% of people who develop MH after exposure to a trigger drug IMannosidosis still may die even with proper medication and care. Among those who do survive, some are disabled due to Definition kidney, muscle, or brain damage. The best prognosis Mannosidosis is a rare inherited disorder, an inborn exists for people with definite or suspected MH suscep- error of metabolism, that occurs when the body is unable tibility who are able to prevent exposures to trigger to break down chains of a certain sugar (mannose) prop- drugs by discussing their history with their doctors. As a result, large amounts of sugar-rich compounds Improved genetic testing in the future may help identify build up in the body cells, tissues, and urine, interfering most or all people with inherited MH susceptibility, so with normal body functions and development of the they too may prevent exposures that could trigger MH skeleton. Description Resources Mannosidosis develops in patients whose genes are BOOKS unable to make an enzyme required by lysosomes (struc- Hopkins, Philip M. Hyperthermic tures within the cell where proteins, sugars, and fats are and Hypermetabolic Disorders: Exertional Heat Stroke, broken down and then released back into the cell to make Malignant Hyperthermia and Related Syndromes.
However generic tadalafil 10 mg with visa erectile dysfunction types, in approx- come from the early gamete cell will also have the alter- imately 10% of women who are carriers for the altered ation cheap 5mg tadalafil otc erectile dysfunction causes anxiety. The People with PAIS also have primary amenorrhea, and amount of cells with altered receptors and the location of breast development occurs in puberty. Unlike CAIS, those cells within the body will determine how severely affected individuals in the same family with presum- affected a person will be. As a result, some affected Mutations within the androgen receptor gene are people may be raised as females whereas others may be also responsible for the neuromuscular condition spinob- raised as males. See sepa- structure of the genitals, the surgical correction needed, rate entry for more information. Demographics Complete androgen insensitivity syndrome occurs Mild androgen insensitivity in approximately 1/64,000 46,XY births or 2-5/100,000 births overall. Partial AIS is at least as common as Males with mild androgen insensitivity usually have complete AIS. The incident of mild AIS is unknown, normal male genitals and internal male structures. During but is estimated to account for approximately 40% puberty, males with MAIS may have breast enlargement, of male infertility due to severe oligospermia or azo- sparse facial and body hair, and small penis. As with CAIS, affected men within the Signs and symptoms same family usually have similar features. Complete androgen insensitivity Diagnosis Individuals with CAIS are born looking like normal female babies. Often, the condition is discovered in one Diagnosis is usually made based upon clinical fea- of two ways. The child can have an inguinal hernia that tures, chromosome analysis, hormone levels, and analy- upon repair is found to contain testicles. Chromosome analysis reveals normal male chro- Affected individuals have a short, blind ending vagina mosomes. Affected individuals can have elevated and no uterus, cervix, fallopian tubes, or ovaries. During luteinizing hormone, normal to slightly elevated testos- puberty, some girls will have absent or decreased sexual terone, and high estradiol for men. Breasts develop normally and can be large in size hormone may also be normal to elevated. People with androgen receptor function in skin fibroblast cells is also CAIS are usually raised as females and have normal used to aid in a diagnosis. All women with CAIS are ster- As of 2001, direct genetic testing for molecular ile. In families with CAIS, all affected members will have defects in the androgen receptor gene is being done on a complete androgen insensitivity and similar physical research basis only. Partial androgen insensitivity syndrome Treatment and management Children with PAIS usually present at birth due to Complete androgen insensitivity ambiguous genitalia. The genitalia can look like female genitals with some masculinization, completely Treatment of CAIS requires the removal of the testi- ambiguous genitals where the sex of the baby cannot be cles from the pelvis or inguinal canal to decrease risk of immediately determined, or male genitals with some testicular malignancy. The degree of severity is a direct result of nancy is approximately 5% and rarely occurs before age the degree of severity of the genetic alteration in the 25, the testicles are usually removed after the develop- androgen receptor and resulting amount of functional ment of the secondary sex characteristics, as the testes androgen receptor. After the removal of the same as CAIS, with absent fallopian tubes, cervix, the testes, estrogen supplementation is started to aid in GALE ENCYCLOPEDIA OF GENETIC DISORDERS 85 the development of secondary sex characteristics and to Intersex Society of North America. Reconstructive sur- Carin Lea Beltz, MS, CGC gery of the genitals and lengthening of the vagina may be necessary. People with PAIS raised as boys may need surgery to improve the appearance of the genitals. Androgen sup- plementation may be implemented, though long-term IAnemia, sideroblastic affects of androgen therapy are not known. Definition X-linked sideroblastic anemia is a hereditary Mild androgen insensitivity enzyme disorder in which the body has adequate iron but Males with MAIS may require no treatment at all or is unable to incorporate it into hemoglobin. Males who are infertile may benefit from assisted reproductive tech- Description nologies. X-linked sideroblastic anemia is the hereditary form of sideroblastic anemia, also known as iron overload ane- Prognosis mia or sideroblastosis. Another, more common type of sideroblastic anemia is called acquired sideroblastic For CAIS and MAIS, the prognosis is excellent. Generally, gender assignment is not difficult and sexual orientation is female for CAIS and male for MAIS. In sideroblastic anemia, iron enters a developing red Treatment usually involves minimal surgery and hor- blood cell and is not incorporated properly into the hemo- mone supplementation. This causes prognosis is very dependent upon the severity of the con- iron to accumulate in the mitochondria and sideroblasts. Assignment of gender can be difficult and genital The defective hemoglobin then transports oxygen poorly, surgery can be more involved.
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