Tangier disease is an inherited metabolic condition. It occurs due to a problem with an enzyme that processes cholesterol. This can cause an accumulation of toxic cholesterol in certain body tissues.
Metabolic diseases are a group of conditions that disrupt a normal metabolic pathway. This typically refers to the process of converting food to energy. Usually, these processes rely on the actions of enzymes, which are special proteins that speed up these reactions.
With Tangier disease, one of these enzymes does not function correctly. This means the body is unable to process cholesterol into high-density lipoprotein (HDL), or good cholesterol. This means toxic levels of cholesterol can build up in tissues. Additionally, this can also increase the risk of other health problems, as HDL can help reduce the risk of cardiovascular disease.
Tangier disease is a genetic condition that occurs due to a problem with an enzyme. This enzyme plays an important role in the metabolic pathway of processing cholesterol and certain fats known as phospholipids.
As such, not only does the condition cause high levels of toxic cholesterol to accumulate in certain tissues, but it also results in low levels of circulating HDL. A buildup of cholesterol can cause enlarged organs and nerve damage, while low levels of HDL can increase the risk of other health problems.
The name of the condition derives from the fact that it was
Other names for Tangier disease include:
- A-alphalipoprotein neuropathy
- alpha HDL deficiency disease
- analphalipoproteinemia
- cholesterol thesaurismosis
- familial hypoalphalipoproteinemia
- HDL lipoprotein deficiency disease
- lipoprotein deficiency disease, HDL, familial
- Tangier disease neuropathy
- Tangier hereditary neuropathy
Tangier disease occurs due to a genetic alteration in the ABCA1 gene. This gene is responsible for producing the ATP-binding cassette transporter A1 protein, or
This enzyme helps transport cholesterol and phospholipids across the cell membrane to the outside of the cell. These substances then combine with another protein, known as apolipoprotein A-I (apoA-I), to create HDL. Also known as good cholesterol, HDL carries cholesterol and phospholipids through the blood from tissues to the liver.
The liver then either redistributes these substances or removes them from the body. The process of removing excess cholesterol from cells is
Prevalence
Tangier disease is a rare condition. At present, researchers have identified roughly 100 cases worldwide. The condition can occur in people of all races. Evidence notes there is a
Inheritance
Tangier disease is an
People with one copy do not typically show symptoms of Tangier disease but may still have lower levels of HDL. This may be due to having a related condition known as familial HDL deficiency.
If both parents are carriers for Tangier disease, they have a 25% chance of having an affected child with each pregnancy. The risk of having a carrier is 50% and the chance of having a child with no gene variation is 25%. The risk is the same for males and females.
Cholesterol is essential for good health. It is necessary for the formation of cell membranes, hormones, and other cellular functions. Two important types of cholesterol are HDL and low-density lipoprotein (LDL).
HDL helps remove excess cholesterol. LDL, however, can deposit cholesterol in arteries, which can negatively affect health. Without sufficient levels of HDL, people are more susceptible to high levels of fats in organs such as the liver, eyes, heart, spleen, and lymph nodes.
As such, symptoms of Tangier disease
- clouding of the outermost layer of the eye
- enlargement of the liver, spleen, and lymph nodes
- enlarged tonsils that may become yellow or orange
- low levels of HDL
- high levels of fat in the blood, known as hypertriglyceridemia
- nerve problems, known as neuropathy
- atherosclerosis
Due to these symptoms, individuals with Tangier disease are also at a higher risk of developing cardiovascular disease and type 2 diabetes.
Diagnosis will typically involve a clinical evaluation and genetic testing. A doctor may suspect Tangier disease if a person presents with signs of the condition, such as yellow-orange tonsils, hepatosplenomegaly, and nerve damage. Blood tests showing high levels of fat and low levels of HDL and apoA-I also indicate the condition.
To confirm a diagnosis of Tangier disease, a doctor will usually recommend
Currently, there is no specific treatment for Tangier disease. Treatment options are typically supportive and will depend on the symptoms a person is experiencing. For example, this may include the surgical removal of the spleen, tonsils, or other enlarged organs.
Management of the condition will often focus on reducing the risk of cardiovascular disease. This may involve following a low fat dietary pattern and overall healthy lifestyle. A person may require regular assessments for nerve damage and vision changes.
Tangier disease is a genetic metabolic disease. It occurs due to problems with the ATP-binding cassette transporter A1 (ABCA1) protein. This enzyme helps transport cholesterol out of cells, where it then turns into good cholesterol, also known as high-density lipoprotein (HDL).
When this enzyme does not function correctly, it can cause toxic cholesterol to build up in cells. It can also cause low levels of HDL. This can manifest as organ enlargement, nerve damage, and a higher risk of cardiovascular disease.
There is no specific treatment for Tangier disease. However, managing the condition may involve dietary changes and removal of enlarged organs.