Makindo Medical Notes

Related Subjects: |Refsum's disease |Abetalipoproteinaemia

About

• Abetalipoproteinemia is also known as Bassen-Kornzweig syndrome, a rare inherited disorder affecting fat absorption and metabolism.
• The condition is caused by mutations in the microsomal triglyceride transfer protein (MTP), which plays a crucial role in the assembly and secretion of lipoproteins containing apolipoprotein B.

Aetiology

• It is an autosomal recessive disorder caused by a deficiency in apolipoprotein B-containing lipoproteins, including chylomicrons, VLDL, and LDL.
• Prevents the normal absorption and transport of fats and fat-soluble vitamins (A, D, E, K) from the intestines.
• Due to impaired lipid absorption, patients develop a deficiency in essential fat-soluble vitamins, leading to multisystemic complications.

Clinical Features

• Starts in infancy with gastrointestinal symptoms such as chronic diarrhoea and fat malabsorption.
• Neurological symptoms like gait ataxia, muscle weakness, and nystagmus become evident early in life.
• Retinitis pigmentosa, degeneration of the retina with visual impairment.
• Normal cognitive development (IQ is unaffected).
• Other common findings include loss of deep tendon reflexes, muscle weakness, and pigmentary retinal degeneration.

Investigations

• Blood tests: Low total cholesterol and Triglyceride levels. Absent/low low-density lipoprotein (LDL) and chylomicrons.
• Blood smear: Shows the presence of acanthocytes (abnormally shaped red blood cells).
• Genetic testing: Can confirm mutations in the MTP gene, which encodes microsomal triglyceride transfer protein.

Management

• Vitamin E supplementation: High doses of vitamin E can slow neurological damage and other complications.
• Other fat-soluble vitamins: Vitamins A, D, and K needed to prevent deficiency-related complications such as vision loss, bone abnormalities, and clotting disorders.
• Dietary management: A low-fat diet may be recommended to reduce gastrointestinal symptoms, combined with the use of medium-chain triglycerides (MCTs) for better fat absorption.

Prognosis

• With early diagnosis and appropriate vitamin supplementation, many complications, particularly neurological ones, can be mitigated. However, some issues, such as retinal degeneration, may still progress.