Abetalipoproteinemia

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 both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.

Abetalipoproteinemia on Wikipedia

'''Abetalipoproteinemia''' is a rare genetic disorder that interferes with the normal absorption of fat and fat soluble vitamins from food.

Features

This disorder leads to a multiple vitamin deficiency, affecting the fat soluble Retinol, vitamin D, Tocopherol, and vitamin K. However, many of the observed effects are due to vitamin E deficiency in particular.

Diagnosis

The inability to absorb fat in the ileum will result in steatorrhea, or fat in the stool. As a result, this can be clinically diagnosed when foul smelling stool is encountered. Low plasma chylomicron levels are also characteristic.

Pathophysiology

Two genes have been identified in which mutations are associated with this disorder: microsomal triglyceride transfer protein (MTT) and apolipoprotein B (ApoB). There is an absence of betalipoprotein B. On intestinal biopsy, vacuoles containing lipids are seen in enterocytes. Since there is no or little assimilation of chylomicrons, their levels in Blood plasma remains low.

Treatment

Treatment with Vitamin E is recommended.

References

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External Resources

Yahoo! Groups: Abetalipoproteinemia - Discussion group for people diagnosed with abetalipoproteinemia.