Abetalipoproteinemia (also known as Bassen-Kornzweig syndrome) is an inherited disorder that affects how fats are made and used in the body. The body needs fats for healthy nerves, muscles, and digestion. Like oil and water, fats can't travel in the blood around the body by themselves-they just don't mix in. Fats attach to special proteins called lipoproteins to travel to wherever they're needed.
Because of a genetic disorder, people with abetalipoproteinemia don't produce a critical "building block" (a special protein) for making lipoproteins. Without enough lipoproteins, fats can't be digested properly or travel around the body to where they're needed, which leads to serious health problems.
Who gets it?
Because of the serious problems caused by lack of fats, abetalipoproteinemia becomes apparent in infancy. Boys seem to be affected more often (70% of the time) than girls. It is inherited, but it is autosomal recessive, meaning both parents have to have the faulty gene for the disorder in order for their child to develop it.
What are the symptoms?
Babies born with abetalipoproteinemia have stomach problems because the body can't digest fats properly. They have abnormal stools which are pale colored and foul-smelling. They have vomiting, diarrhea, bloated bellies, and don't gain weight or grow like they should (failure to thrive).
Because the body has problems with fats, there are also problems with the vitamins that stored in fats: vitamin A, vitamin E, and vitamin K. During the child's first ten years of life, problems caused by the lack of fats and fat-soluble vitamins begin to show. Some of these symptoms are:
- Sensory disturbances - problems with sensing temperature and touch, especially in the hands and feet (hypesthesia)
- Trouble walking (ataxia) - affects 33% of children by 10 years of age, gets worse over time
- Movement disorders - tremors, shaking (chorea), trouble reaching for things (dysmetria), trouble talking (dysarthria)
- Muscle problems - weakness, shortening (contraction) of muscles in the back that causes the spine to curve (kyphoscoliosis)
- Blood problems - low iron (anemia), problems with clotting, abnormal red blood cells (acanthocytosis)
- Eye problems - night blindness, poor eyesight, problems with eye control (ophthalmoplegia), cataracts
How is it diagnosed?
The first clues will be the infant's stomach problems. His stool when tested will show a high level of fat (the fat is being eliminated rather than being used by the body). Blood tests can help with the diagnosis. The abnormal red blood cells present in abetalipoproteinemia can be seen under a microscope. Also, there will be very low levels of fats like cholesterol and triglycerides in the blood. Tests for clotting time and iron levels will also be abnormal. An eye exam might show inflammation of the back of the eye (retinitis). Testing of muscle strength and contractions may have abnormal results as well.
How is it treated?
A specific diet for people with abetalipoproteinemia has been developed. There are several requirements in the diet, including avoiding eating certain types of fats (long-chain triglycerides) in favor of eating other types (medium-chain triglycerides). Another requirement is adding doses of vitamin supplements containing vitamins A, E, and K, as well as iron. A nutritionist works with the child and family affected by abetalipoproteinemia to design meal plans that meet these special dietary needs.
What is the future?
Abetalipoproteinemia has provided researchers with important insights into how fats and lipoproteins work in the body. Now that they have identified that a genetic defect is at the heart of the disorder, researchers are working on identifying the particular gene involved. Perhaps as the science of genetics improves and evolves, scientists will one day be able to identify people who carry the faulty gene, and maybe even correct the defect to prevent the disorder.
Information for this article was taken from:
- Berriot-Varoqueaux, N., Aggerbeck, L. P., Samson-Bouma, M., & Wetterau, J. R. (2000). The role of the microsomal triglyceride transfer protein in abetalipoproteinemia. Annu Rev Nutr, vol. 20, pp 663-697.
- Gregg, R. E., Wetterau, J. R., Berriot-Varoqueaux, N., Aggerbeck, L. P., & Samson-Bouma, M. (1994). The molecular basis of abetalipoproteinemia. Curr Opin Lipidol, vol. 5, no. 2, pp 81-86.
- Rader, D. J., Brewer, H. B., Jr., Gregg, R. E., Wetterau, J. R., Berriot-Varoqueaux, N., Aggerbeck, L. P., Samson-Bouma, M., & Wetterau, J. R. (1993). Abetalipoproteinemia: New insights into lipoprotein assembly and vitamin E metabolism from a rare genetic disease. JAMA, vol. 270, no. 7, pp 865-869.
- Stone, N. J., Blum, C. B., & Winslow, E. (1998). Pathophysiology of hyperlipoproteinemias. In Management of Lipids in Clinical Practice. Available online at Medscape.
