Tangier disease: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
Tangier disease is a disorder of lipid metabolism where cholesterol efflux from reticulo-endothelial cells is impaired resulting in absent to severely decreased HDL. Cholesterol esters accumulates in macrophages which leads deposition of foam cells in several tissues. | |||
[[High-density lipoproteins]] are created when a protein in the bloodstream, [[apolipoprotein A1]] ([[apoA1]]), combines with [[cholesterol]] and phospholipids. The cholesterol and phospholipids used to form HDL originate from inside cells but is transported out of the cell into the blood via the [[ABCA1]] transporter. People with Tangier disease have defective [[ABCA1]] transporters resulting in a greatly reduced ability to transport cholesterol out of their cells, which leads to an accumulation of cholesterol in many body tissues. Reduced blood levels of high-density lipoproteins is sometimes described as [[hypoalphalipoproteinemia]]. | [[High-density lipoproteins]] are created when a protein in the bloodstream, [[apolipoprotein A1]] ([[apoA1]]), combines with [[cholesterol]] and phospholipids. The cholesterol and phospholipids used to form HDL originate from inside cells but is transported out of the cell into the blood via the [[ABCA1]] transporter. People with Tangier disease have defective [[ABCA1]] transporters resulting in a greatly reduced ability to transport cholesterol out of their cells, which leads to an accumulation of cholesterol in many body tissues. Reduced blood levels of high-density lipoproteins is sometimes described as [[hypoalphalipoproteinemia]]. | ||
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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. | 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. | ||
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==Epidemiology and Demographics== | ==Epidemiology and Demographics== | ||
* Tangier disease is a rare disorder with approximately 50 cases identified worldwide. | * Tangier disease is a rare disorder with approximately 50 cases identified worldwide. | ||
Revision as of 15:05, 11 September 2013
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2] Twinkle Singh, M.B.B.S. [3]
Synonyms and keywords: Familial alphalipoprotein deficiency, HDL deficiency - familial, high density lipoprotein deficiency, analphalipoproteinaemia, high density lipoprotein deficiency - type 1, high density lipoprotein deficiency - Tangier type
Overview
Tangier disease is a rare autosomal recessive disorder characterised by severely decreased high-density lipoprotein (HDL), often referred to as "good cholesterol" in the bloodstream, caused by defective cholesterol efflux from macrophages. It manifests with enlarged and orange coloured tonsils, hepatomegaly, splenomegaly, peripheral neuropathy and vision changes.
Historical Perspective
Tangier disease (TD) is named after Tangier Island, Virginia. In 1959 a five year old patient named Teddy Laird from that island, presented with strikingly large and yellow-orange tonsils, which were removed. Initially it was diagnosed as Niemann-Pick disease but a further investigation revealed an extremely high number of cholesterol filled macrophages (foam cells) in several other tissues, which included bone marrow and spleen. Presence of similar symptoms in his sister and discovery of very low HDL cholesterol in both the sister and parents of Teddy led to establishment of genetic basis of the disease. Later on several other residents of the same island were found to have markedly reduced HDL. Since then only 100 cases of Tangier disease have been diagnosed.
Pathophysiology
Tangier disease is a disorder of lipid metabolism where cholesterol efflux from reticulo-endothelial cells is impaired resulting in absent to severely decreased HDL. Cholesterol esters accumulates in macrophages which leads deposition of foam cells in several tissues.
High-density lipoproteins are created when a protein in the bloodstream, apolipoprotein A1 (apoA1), combines with cholesterol and phospholipids. The cholesterol and phospholipids used to form HDL originate from inside cells but is transported out of the cell into the blood via the ABCA1 transporter. People with Tangier disease have defective ABCA1 transporters resulting in a greatly reduced ability to transport cholesterol out of their cells, which leads to an accumulation of cholesterol in many body tissues. Reduced blood levels of high-density lipoproteins is sometimes described as hypoalphalipoproteinemia.
Genetics
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Mutations in the chromosome 9q31 lead to a defective ABCA1 transporter. 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 (CAD).
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.
Epidemiology and Demographics
- 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.
Natural History, Complications and Prognosis
- Premature atherosclerosis
- Coronary heart disease
Diagnosis
History
- History of similar complaints in any of the family members should be inquired.
Symptoms
- Vision disturbances - due to clouding of the cornea
- Abdominal pain
- Neuropathy - tingling sensation in the fingers, pins and needle sensation, weakness
Physical Examination
Eye
- Hazy cornea
Throat
- Enlarged tonsils that appear orange or yellow.
Abdomen
Laboratory Findings
- Lipid panel shows
- Slightly elevated amounts of fat in the blood (mild hypertriglyceridemia)
- Reduced HDL
- Low total cholesterol
References
External links
- Tangier disease at NLM Genetics Home Reference