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Malignant hyperthermia is a condition in which a patient experiences a severe reaction to surgical and invasive procedure drugs. Malignant hyperthermia triggers can include some anesthetic gases used to block the feeling of pain, and certain muscle relaxants used to temporarily paralyze the patient. When patients with this disorder are administered these drugs, they can experience a variety of symptoms and complications. If these symptoms and complications are not promptly treated they can be life-threatening.
Some patients are said to be susceptible to this disorder. This disorder commonly occurs alone, but it can also occur as a complication of certain inherited muscle diseases, such as multiminicore disease and central core disease.
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How Common is this Genetic Disorder?
Approximately one in 5,000 to 50,000 people experience malignant hyperthermia when given anesthetic gases. Susceptibility to this condition is most likely more common, but the exact incidence rate is unknown because those who are known to be at an increased risk for malignant hyperthermia are never exposed to malignant hyperthermia triggers.
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Genetics of Malignant Hyperthermia
Variations occurring in the RYR1 and CACNA1S genes are what heighten a person's risk of developing this condition. RYR1 gene mutation are responsible for most cases of this condition, referred to as MHS1. Less than one percent of all malignant hyperthermia susceptibility cases are caused by the types known as MHS5, which results from CACNA1S gene mutations.
An autosomal dominant inheritance pattern is responsible for this condition. Most patients have a parent who is at risk for malignant hyperthermia, and inherit an altered gene from them.
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Symptoms of Malignant Hyperthermia
The symptoms associated with this disorder can be serious and include:
- Quick increase in temperature to 105 degrees Fahrenheit or more
- Dark brown urine
- Muscle stiffness and rigidity
- Aching muscles without an obvious cause
Complications can also occur that are serious and they include:
- Breakdown of muscle tissue
- Kidney failure
- Weak muscles
- Metabolic acidosis
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Diagnosing this Genetic Disorder
This disorder is often first seen after the patient has been administered anesthesia for a surgical procedure. Patients may also have a family history of this disorder or of family members dying without explanation under anesthesia. The patient may have an irregular heart rate and rapid heart rate. The diagnostic tests that may be done include:
- Genetic testing to see if the RYR1 gene is defective
- Myoglobin in the urine
- Muscle biopsy
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How is Malignant Hyperthermia Treated?
When the patient is experiencing an episode of this condition, they will be wrapped in a cooling blanket to help reduce their temperature as well as the chance for serious complications. Heart rhythm problems can sometimes be treated using drugs, such as lidocaine, dantrolene, or beta-blockers. During an acute episode, kidney function can be maintained by intravenously administering fluids and certain medications.
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Genetics Home Reference. (2010). Malignant Hyperthermia. Retrieved on June 24, 2010 from Genetics Home Reference: http://ghr.nlm.nih.gov/condition/malignant-hyperthermia
Medline Plus. (2009). Malignant Hyperthermia. Retrieved on June 24, 2010 from Medline Plus: http://www.nlm.nih.gov/medlineplus/ency/article/001315.htm
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