Abetalipoproteinemia, or Bassen-Kornzweig syndrome, is a rare autosomal recessive disorder that interferes with the normal absorption of fat and fat-soluble vitamins from food. It is caused by a deficiency of apolipoprotein B-48 and B-100, which are used in the synthesis and exportation of chylomicrons and VLDL respectively. It is not to be confused with familial dysbetalipoproteinemia.
Abetalipoproteinemia 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. This leads to a multiple vitamin deficiency, affecting the fat-soluble vitamin A, vitamin D, vitamin E, and vitamin K. However, many of the observed effects are due to vitamin E deficiency in particular.
The signs and symptoms of abetalipoproteinemia appear in the first few months of life(because pancreatic lipase is not active in this period). 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). The stool may contain large chunks of fat and/or blood. 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(due to deficiency of Vitamin A,retinol). 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 typically results in eye problems with degeneration of the spinocerebellar and dorsal columns tracts.
Often symptoms will arise that indicate the body is not absorbing or making the lipoproteins that it needs. These symptoms usually appear en masse, meaning that they happen all together, all the time. These symptoms come as follows:
- Failure to grow in infancy
- Fatty, pale stools
- Frothy stools
- Foul smelling stools
- Protruding abdomen
- Mental retardation/developmental delay
- Dyspraxia, evident by age ten
- Muscle weakness
- Slurred speech
- Scoliosis (curvature of the spine)
- Progressive decreased vision
- Balance and coordination problems
- Retinitis Pigmentosa
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