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| DiseaseID |
HGD37 |
| Genetic
Disorder |
Tangier disease
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| Gene
Name |
ABC1 (ATP-binding cassette) gene |
| Description |
Tangier disease (TD) is a genetic disorder of cholesterol transport named for the secluded island of Tangier, located off the coast of Virginia. TD was first identified in a five-year-old inhabitant of the island who had characteristic orange tonsils, very low levels of high density lipoprotein (HDL) or 'good cholesterol', and an enlarged liver and spleen.
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| Symptoms |
The symptoms of Tangier disease are quite variable but the most common symptoms of Tangier disease are enlarged, yellow-colored tonsils, an enlarged spleen, accumulation of cholesterol in the mucous membranes of the intestines, abnormalities in the nervous system (neuropathy), and an increased risk of arteriosclerosis. Less commonly seen symptoms are an enlarged liver, lymph nodes and thymus, and hemolytic anemia. Cholesterol accumulation has been seen in other organs such as the bone marrow, gall bladder, skin, kidneys, heart valves, ureters, testicles, and the cornea of the eye.
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| Causes |
TD is caused by mutations in the ABC1 (ATP-binding cassette) gene on chromosome 9q31. ABC1 codes for a protein that helps rid cells of excess cholesterol. This cholesterol is then picked up by HDL particles in the blood and carried to the liver, which processes the cholesterol to be reused in cells throughout the body. Individuals with TD are unable to eliminate cholesterol from cells, leading to its buildup in the tonsils and other organs. |
| Diagnosis |
Tangier disease is diagnosed through assessment of clinical symptoms and biochemical testing. A diagnosis of Tangier disease should be considered in anyone with deposits of cholesterol on the cornea, an unexplained enlarged spleen or liver, or neurological abnormalities. Examination of the throat and tonsils and rectal mucous membrane should be performed on those suspected to have Tangier disease. Measurements of the total cholesterol, HDL-C, LDL-C, ApoA-1 and triglycerides should also be performed. Patients with Tangier disease have virtually no HDL-C in their bloodstream and ApoA-1 levels are reduced to one to three percent of normal. LDL-C levels are also reduced to approximately 40% of normal and triglyceride levels can be mildly elevated. As of 2001, DNA testing for Tangier disease is not available through clinical laboratories, although DNA testing on a clinical basis should be available in the future. Some laboratories may identify ABCA1 gene changes in patients as part of their research. Prenatal testing is only available if ABCA1 gene changes are identified in the parents.
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| Treatment |
There is no treatment for Tangier disease and treatment of decreased HDL-C with medication is usually ineffective. Occasionally organs such as the spleen and tonsils are removed because of extensive accumulation of cholesterol. Arteriosclerosis may be treated through angioplasty or bypass surgery. Angioplasty involves inserting a small, hollow tube called a catheter with a deflated balloon through the groin or arm and into a clogged artery. The balloon is then inflated which enlarges the artery and compresses the blockage. Coronary artery disease can also be treated through bypass surgery, which is performed by taking a blood vessel from another part of the body and constructing an alternate path around the blocked part of the artery |
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