Tangier disease, also known as familial alpha lipoprotein deficiency, is an extremely rare, inherited condition that was first described in a child on Tangier Island, an island located off of the coast of Virginia. People who have this condition have very low HDL cholesterol levels due to a mutation in a gene called ABCA1. This gene helps to make a protein that helps get rid of excess cholesterol from inside the cell.
When this protein is working properly, cholesterol is shuttled outside of the cell and binds to apolipoprotein A. This forms HDL, or “good” cholesterol, which will travel to the liver so that cholesterol can be recycled. Without this protein, cholesterol will remain inside of the cells and begin to accumulate within them.
Tangier disease is usually noted in childhood. The symptoms of Tangier disease can range from very severe to very mild and depends on whether or not you have one or two copies of the mutated gene.
People who are homozygous for this condition have mutations in both copies of the ABCA1 gene that codes for the protein and have virtually no HDL cholesterol circulating in the blood. These people will also have other symptoms as a result of cholesterol accumulation within various cells in the body, including:
- Neurological abnormalities, which include peripheral neuropathy, decreased strength, loss of pain or heat sensation, muscle pain
- Clouding of the cornea
- Enlarged lymph nodes
- Gastrointestinal symptom, such as diarrhea and abdominal pain
- Appearance or yellow patches on the intestinal mucosa, including the rectum
- Enlarged, yellow-orange tonsils
- Enlarged liver
- Enlarged spleen
- Premature cardiovascular disease
People who are classified as having heterozygous Tangier disease, on the other hand, only have one copy of the mutated gene. They also have roughly half of the normal amount of HDL circulating in the blood. Although people who are heterozygous for this condition usually experience very mild to no symptoms, they are also at risk for premature cardiovascular disease due to the increased risk of developing atherosclerosis. Additionally, anyone who is diagnosed with this disease may pass this medical condition along to their children.
A lipid panel will be performed by your healthcare provider in order to examine the levels of cholesterol circulating in your blood. If you have Tangier disease, this test would reveal the following findings:
- HDL cholesterol levels less than 5 mg/dL in homozygous individuals
- HDL cholesterol between 5 and 30 mg/dL in heterozygous individuals
- Low total cholesterol levels (ranging between 38 and 112 mg/dL)
- Normal or elevated triglycerides (ranging between 116 and 332 mg/dL)
- Levels of apolipoprotein A may also be low to nonexistent.
In order for Tangier disease to be diagnosed, your healthcare provider will examine the results of your lipid panel and will also consider the signs and symptoms you are experiencing. If you have a family history of Tangier disease, your healthcare provider will also take this into account.
Because of the rarity of this disease, there are currently no treatments available for this condition. Medications that boost HDL cholesterol—both approved and experimental—do not appear to increase HDL levels in people with Tangier disease. Following a healthy diet that is low in saturated fat is recommended. Surgeries may be necessary based upon the symptoms experienced by the individual.