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What is Abetalipoproteinemia?
Abetalipoproteinemia is a rare, autosomal recessive genetic disorder that severely affects the digestion and absorption of dietary fats, fat-soluble vitamins and cholesterol. In other words, it is a disorder of fat metabolism. Patients suffering from this disorder fail to make some lipoproteins essential for carrying fat and fat like matters such as cholesterol in the blood. Patients miss a group of lipoproteins known as beta lipoproteins.
Since the body cannot make beta-lipoproteins, it results in severely reduced absorption of dietary fat and fat-soluble vitamins such as vitamins A, D, E, and K from the digestive system to the bloodstream. For normal growth and development of body cells and tissues, a certain level of fats, cholesterols and vitamins are required.
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Signs and Symptoms:
Some of the more common signs and symptoms of abetalipoproteinemia are seen in the first few months of life, including:
- Failure to gain weight
- Abnormal star shaped RBC (acanthocytosis)
- Fatty, foul-smelling stools (steatorrhea)
In addition, other signs and symptoms develop later in childhood and may upset the function of the nervous system. Disruption in the nervous system may lead to poor muscle coordination and difficulty with balance and movement. Individuals experiencing these problems may also develop an eye disorder, called retinitis pigmentosa, in which subsequent degeneration of the light-sensitive layer (retina) at the back of the eye can cause loss of vision. Adults in their middle age may face difficulty in balancing and walking. Many of the disorders associated with Abetalipoproteinemia result due to severe Vitamin E deficiency.
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What Gene is Responsible for Abetalipoproteinemia?
Mutations in a particular gene, called the MTTP (microsomal triglyceride transfer protein) gene, cause the disorder. MTTP gene is located on the (q) arm of chromosome 4 at position 24. MTTP gene sends instructions for making a protein, called microsomal triglyceride transfer protein essential for creating beta-lipoproteins. These proteins are essential for the absorption of fats, fat-soluble vitamins and cholesterol from the diet and then the transportation of these substances to the bloodstream. Therefore, a lack of beta-lipoproteins causes both nutritional and neurological problems in people suffering from Abetalipoproteinemia.
Is Abetalipoproteinemia an inheritable disorder?
Yes, it is an inheritable disorder, but the inheritance pattern is autosomal recessive. It means traits are transmitted to both the sexes and both can be carriers as well. So the affected persons (homologous for the gene) have parents and offsprings who are unaffected (heterozygous) carriers.
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Diagnosis of Abetalipoproteinemia:
Diagnosis of this disorder is very challenging, as the condition is rarely seen in the clinical practice. However, careful assessment of signs and symptoms, with pedigree analysis are helpful. But laboratory testing and genetic analysis are must.
Treatment of Abetalipoproteinemia:
The main goal of any patient suffering from Abetalipoproteinemia is to get early treatment with dietary changes and Vitamin supplementation. In addition, treatment is supported by referral to neurologist, gastroenterologist, ophthalmologist and a dietitian.
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(Web): What is abetalipoproteinemia? -- http://ghr.nlm.nih.gov/condition/abetalipoproteinemia
(Web): Abetalipoproteinemia -- http://rarediseases.info.nih.gov/GARD/Condition/5/Abetalipoproteinemia.aspx
(Web): Childhood Ataxia -- http://pediatrics.uchicago.edu/chiefs/documents/ChildhoodAtaxia.pdf
(Web): Abetalipoproteinemia -- https://online.epocrates.com/noFrame/showPage.do?method=diseases&MonographId=471&ActiveSectionId=11