Abetalipoproteinemia
Description
Abetalipoproteinemia is a rare, inherited disorder that affects the body‘s ability to transport fat. This condition is caused by a deficiency in the production of apolipoprotein B (apoB), a protein crucial for the formation of lipoproteins, which are responsible for carrying cholesterol and triglycerides in the bloodstream. Without apoB, fats cannot be effectively transported throughout the body, leading to a range of health complications.
Genes Involved
Abetalipoproteinemia is caused by mutations in the MTTP gene, which provides instructions for making the microsomal triglyceride transfer protein (MTP). MTP is essential for the assembly and secretion of very-low-density lipoproteins (VLDL), which carry triglycerides from the liver to other tissues.
Recognizing the Signs and Symptoms
The signs and symptoms of abetalipoproteinemia typically become apparent in infancy or early childhood. Common symptoms include:
- Malabsorption: Difficulty absorbing fats, leading to diarrhea, steatorrhea (fatty stools), and failure to thrive.
- Hypolipidemia: Low levels of cholesterol and triglycerides in the blood.
- Acanthocytosis: Abnormal red blood cells with spiky projections.
- Neurological problems: Including retinitis pigmentosa (a condition that damages the retina), progressive cerebellar ataxia (loss of coordination), and peripheral neuropathy (nerve damage in the limbs).
- Vitamin E deficiency: Can cause serious neurological problems, including muscle weakness, incoordination, and problems with balance.
Causes
Abetalipoproteinemia is caused by inherited mutations in the MTTP gene. Both parents must carry the mutated gene for their child to inherit the condition. This means abetalipoproteinemia is an autosomal recessive disorder, meaning a person must inherit two copies of the mutated gene, one from each parent, to have the condition.
Inheritance/recurrence risk
Since abetalipoproteinemia is an autosomal recessive disorder, if both parents are carriers of the mutated gene, there is a 25% chance with each pregnancy of having a child with the disorder. There is a 50% chance of having a child who is a carrier, and a 25% chance of having a child who does not carry the mutated gene.
