Abetalipoproteinemia
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What is abetalipoproteinemia?Abetalipoproteinemia is an inherited disorder that affects the absorption of dietary fats, cholesterol, and certain vitamins. People affected by this disorder are not able to make certain lipoproteins, which are molecules that consist of proteins combined with cholesterol and particular fats called triglycerides. These lipoproteins, referred to as beta-lipoproteins, include low-density lipoproteins (LDL), very-low-density lipoproteins (VLDL), and chylomicrons. A lack of beta-lipoproteins prevents absorption through the digestive tract of dietary fats and fat-soluble vitamins such as vitamins E, A, and sometimes K. Sufficient levels of fats, cholesterol, and vitamins are necessary for normal growth, development, and maintenance of the body's cells and tissues, particularly nerve cells and tissues in the eye. The signs and symptoms of abetalipoproteinemia appear in the first few months of life. They can include failure to gain weight and grow at the expected rate (failure to thrive); diarrhea; abnormal star-shaped red blood cells (acanthocytosis); and fatty, foul-smelling stools (steatorrhea). Other features of this disorder may develop later in childhood and often impair the function of the nervous system. They can include poor muscle coordination, difficulty with balance and movement (ataxia), and progressive degeneration of the light-sensitive layer (retina) at the back of the eye that can progress to near-blindness. Adults in their thirties or forties may have increasing difficulty with balance and walking. Many of the signs and symptoms of abetalipoproteinemia result from a severe vitamin deficiency, especially vitamin E deficiency, which can lead to the nerve problems associated with this disorder. How common is abetalipoproteinemia?Abetalipoproteinemia is a rare disorder with approximately 100 cases described worldwide. What genes are related to abetalipoproteinemia?Mutations in the MTTP gene cause abetalipoproteinemia. The MTTP gene provides instructions for making a protein called microsomal triglyceride transfer protein, which is essential for creating beta-lipoproteins. These lipoproteins are necessary for the absorption of fats, cholesterol, and fat-soluble vitamins from the diet and the efficient transport of these substances in the bloodstream. Most of the mutations in this gene lead to the production of an abnormally short microsomal triglyceride transfer protein, which prevents the normal creation of beta-lipoproteins in the body. How do people inherit abetalipoproteinemia?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.
Source: National Institutes of Health
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Recent studies from Hacettepe University add new data to liver disease
2007 APR 16 -- New research, "Hepatosteatosis with hypobetalipoproteinemia," is the subject of a report. According to recent research from Ankara, Turkey, "Nonalcoholic fatty liver disease is increasingly recognized as a condition that may progress to chronic liver disease. Most cases of fatty liver are asymptomatic and often are detected during routine medical or laboratory examinations." "There also are some rare genetic diseases such as abetalipoproteinemia and familial hypobetalipoproteinemia that may cause fatty liver disease. Both are inherited disorders of lipoprotein metabolism. Although abetalipoproteinemia and homozygous familial hypobetalipoproteinemia patients present with severe manifestations, heterozygotes are usually asymptomatic. In the last several years, case reports or studies indicating a relationship between hepatosteatosis and familial heterozygote hypobetalipoproteinemia (FHBL) have been reported," wrote D. Sen and colleagues, Hacettepe University. The researchers concluded: "Here, we report three cases of FHBL with characteristic lipid profile, mildly elevated liver enzymes and hepatosteatosis confirmed by ultrasonography." Sen and colleagues published their study in the Journal of the National Medical Association (Hepatosteatosis with hypobetalipoproteinemia. Journal of the National Medical Association, 2007;99(3):284-6). For additional information, contact D. Sen, Hacettepe University Medical School, Departments of Internal Medicine, Ankara, Turkey. Publisher contact information for the Journal of the National Medical Association is: National Med Association, 1012 10th St., N W, Washingon, DC 20001, USA. Keywords: Turkey, Ankara, Fatty Liver, Liver Disease. This article was prepared by Gastroenterology Week editors from staff and other reports. Copyright 2007, Gastroenterology Week via NewsRx.com.
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