abetalipoproteinemia

Abetalipoproteinemia, also called Bassen Kornzweig disease, is a very rare inherited disorder in which a change in the MTTP gene prevents the body from packaging and moving fats and fat-soluble vitamins. Without working apolipoprotein B, levels of low-density lipoprotein cholesterol stay far below normal. Infants may have poor growth, bulky oily stools, and trouble gaining weight, and later some people develop weak muscles, balance problems, or vision loss because of vitamin shortages. The severity and specific features can vary considerably from person to person. Fewer than one in a million people worldwide are thought to have this autosomal recessive condition.

Severity and symptoms vary widely between individuals. Early signs often relate to poor absorption of dietary fat, including chronic diarrhea, steatorrhea (greasy stools), and failure to thrive despite adequate food intake. Laboratory testing typically shows markedly low LDL and total cholesterol, and blood smears reveal acanthocytosis, a distinctive spiky shape of red blood cells. As children grow, fat-soluble vitamin deficiencies can lead to progressive neurological problems such as areflexia, muscle weakness or myalgia, and in some cases ataxia that affects balance. Vision changes are another hallmark; many individuals develop night blindness (nyctalopia) in childhood followed by gradual loss of peripheral or color vision due to retinal degeneration. Less commonly, anemia, hypoalbuminemia, or hepatomegaly may appear. Not all individuals experience all features, and severity varies considerably.

Abetalipoproteinemia is inherited in an autosomal recessive pattern. The MTTP gene provides instructions for building the microsomal triglyceride transfer protein, which is essential for assembling and releasing lipoproteins that carry fats and fat-soluble vitamins through the bloodstream. When both copies of MTTP carry pathogenic variants, the protein does not function properly, leading to very low apolipoprotein B and disrupted fat transport. A child must receive one altered MTTP gene from each parent to be affected. Parents who each carry a single variant usually have no symptoms but have a 25 percent chance with every pregnancy of having an affected child. Because this condition is more common when parents share a common ancestor, carrier testing can be particularly helpful for extended family members and for couples with shared ancestry who are planning a pregnancy. Genetic counseling is recommended for all families to discuss testing options and reproductive planning.

Currently, management focuses on supportive care and symptom management. Care is typically coordinated by a multidisciplinary team that may include gastroenterologists, neurologists, ophthalmologists, dietitians, and genetic specialists. Long-term management includes regular surveillance for nutritional deficiencies, growth parameters, liver health, neurological function, and vision. Dietary adjustments under professional guidance and close monitoring of fat-soluble vitamin levels help address malabsorption and may slow progression of neurological and visual complications. Patients should discuss personalized management strategies with their healthcare team and consider genetic counseling for family planning.

Outcomes depend on many factors including age at diagnosis, the effectiveness of nutritional support, and access to specialized care. When identified early and followed closely, some individuals maintain good overall health and stable neurologic function, while others experience progressive vision loss or neurological difficulties that impact daily activities. Outcomes described in medical literature continue to evolve as standards of care improve. Families often find it helpful to connect with specialists familiar with this condition and with patient advocacy groups for support and updated information. Genetic counseling can provide guidance for relatives who may be carriers and for future family planning.

Clinical trials are underway exploring new treatment approaches for abetalipoproteinemia. Individuals interested in research participation can search ClinicalTrials.gov or consult their care team about eligibility.