Bassen-Kornzweig syndrome

Overview

Bassen–Kornzweig syndrome, also known as abetalipoproteinemia, is a rare inherited metabolic disorder that affects the body's ability to absorb and transport dietary fats and fat-soluble vitamins. First described in the 1950s by Bassen and Kornzweig, the condition is marked by the absence of apolipoprotein B-containing lipoproteins, such as chylomicrons and very low-density lipoproteins (VLDL). As a result, individuals have fat malabsorption, vitamin deficiencies, and multi-system complications affecting the nervous system, eyes, and red blood cells.

Causes

Bassen–Kornzweig syndrome is caused by mutations in the MTTP gene(microsomal triglyceride transfer protein), which plays a crucial role in assembling and secreting lipoproteins in the intestines and liver.

• The condition is inherited in an autosomal recessive pattern.

• Mutations in both copies of the MTTP gene lead to failure in forming apolipoprotein B-containing lipoproteins.

• Without these lipoproteins, fats and fat-soluble vitamins cannot be properly absorbed or transported.

Symptoms

Symptoms typically begin in infancy or early childhood. They progress if not managed:

• Failure to thrive and poor weight gain

• Steatorrhea (fatty, foul-smelling stools)

• Muscle weakness and fatigue

• Neurological symptoms such as ataxia and peripheral neuropathy

• Retinitis pigmentosa leading to night blindness and vision loss

• Acanthocytosis (spiky red blood cells seen on a blood smear)

• Bleeding tendency due to vitamin K deficiency

Diagnosis

Diagnosis involves identifying clinical features, lab abnormalities, and genetic confirmation:

• Blood tests showing extremely low levels of cholesterol and triglycerides

• Absence or deficiency of apolipoprotein B

• Peripheral blood smear showing acanthocytes

• Low levels of fat-soluble vitamins (A, D, E, K)

• Stool studies confirming fat malabsorption

• Genetic testing confirming MTTP mutations

Treatment

Although there is no cure, early dietary and nutritional interventions can prevent serious complications:

• Low-fat, high-calorie diet supplemented with medium-chain triglycerides (MCTs)

• High doses of fat-soluble vitamins, especially vitamin E, to protect nerves and vision

• Regular monitoring of growth, development, and vitamin levels

• Supportive therapies such as physical therapy for coordination problems

• Genetic counseling for affected families

Prognosis

The long-term outlook depends on how early the condition is detected and treated:

• With early diagnosis and treatment, many complications can be prevented.

• Untreated individuals may develop irreversible neurological and visual impairment.

• Lifelong management is necessary to maintain quality of life and prevent decline.