Tangier disease

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Tangier disease is a rare inherited disorder characterized by a severe reduction in the amount of high density lipoprotein (HDL), often referred to as "good cholesterol," in the bloodstream. High-density lipoproteins are created when a type of protein in the bloodstream, apolipoprotein A1 (apoA1), picks up cholesterol from the cells. People with Tangier disease have a greatly reduced ability to transport cholesterol out of their cells, leading to an accumulation of cholesterol in many body tissues. Reduced blood levels of high-density lipoproteins is sometimes described as hypolipoproteinemia.

People affected by this condition also have slightly elevated amounts of fat in the blood (mild hypertriglyceridemia) and disturbances in nerve function (neuropathy). The tonsils are visibly affected by this disorder; they frequently appear orange or yellow and are extremely enlarged. Affected people often develop premature atherosclerosis, which is characterized by fatty deposits and scar-like tissue lining the arteries. Other signs of this condition may include an enlarged spleen (splenomegaly), an enlarged liver (hepatomegaly), clouding of the cornea, and early-onset cardiovascular disease. How common is Tangier disease?

Tangier disease is a rare disorder with approximately 50 cases identified worldwide. This disorder was originally discovered on Tangier Island off the coast of Virginia, but has now been identified in people from many different countries.

[edit] Genetics

Tangier disease is inherited in an autosomal recessive pattern.

Mutations in the ABCA1 gene cause Tangier disease. The ABCA1 gene provides instructions for making a protein that transports cholesterol and particular fats called phospholipids out of the cells. These mutations prevent the ABCA1 protein from effectively transporting cholesterol and phospholipids out of cells for pickup by ApoA1 in the bloodstream. This inability to transport cholesterol out of cells leads to a deficiency of high-density lipoproteins in the circulation, which is a risk factor for coronary artery disease. Additionally, the buildup of cholesterol in cells can be toxic, causing cell death or impaired function. These combined factors lead to the signs and symptoms of Tangier disease.

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.