Abetalipoproteinemia

Abetalipoproteinemia (ABL) is a rare inherited disorder characterized by difficulty in absorbing fats (lipids) in the intestine.

ABL, also called Bassen-Kornzweig syndrome, is considered a metabolic disorder that results from the absence of apolipoprotein B, necessary for the transport of dietary fat from the small bowel into blood circulation.

Abetalipoproteinemia is a genetic disorder due to mutations in the microsomal triglyceride transfer protein (MTP) located on chromosome 4 (4q23).

ABL is an autosomal recessive disorder. This means that both copies of the MTP gene received from both parents must be mutated to inherit the disorder.

The incidence of abetalipoproteinemia is reported as less than 1 in 1 million. For this reason, it is considered a rare disorder.

The main symptoms of abetalipoproteinemia or Bassen-Kornzweig syndrome are:

• Retinitis pigmentosa:
  • Loss of night vision.
  • Reduced field of vision.
• Neuromuscular impairment:
  • Ataxia: Difficulty with balance and movement.
  • Loss of deep tendon reflexes.
  • Decreased sensation to touch, pain, and temperature.
• Acanthocytosis (abnormally shaped red blood cells) that may result in anemia.

In addition, there are several symptoms related to the abnormal metabolism of the lipids (fats). For example:

• Steatorrhea or fatty stools (too much fat in the feces).
• Diarrhea.
• Fat malabsorption.
• Lipid accumulation in the liver.
• Deficiency of vitamins (A, E or K).
• Vomiting.

It is usually noticed in childhood because infants present with failure to thrive (growth and weight).

In some cases, ABL may cause weakened heart muscle (cardiomyopathy) and severe cases have been reported that resulted in early death.

The presence of star-shaped red blood cells (acanthocytes), with low levels of triglycerides and cholesterol may be a sign of abetalipoproteinemia.

In addition, Vitamin E, LDL-cholesterol, VLDL-cholesterol and apoB lipoprotein are typically undetectable in the blood.

The recommended treatment include:

• A reduction to less than 30% of the dietary fat intake. It is advisable to avoid mainly the consumption of long chain fatty acids.
• The prescription of supplemental doses of fat-soluble vitamins, especially vitamin E (100–200 mg per kg of weight per day) to avoid neurological disabilities and eye disorders.