Abetalipoproteinemia ; Definition, causes, symptoms, Diagnosis, Treatment

Abetalipoproteinemia

Definition

Abetalipoproteinemia is a rare genetic disorder characterized by the inability to synthesize apolipoprotein B (ApoB), leading to impaired lipid absorption and transport.

Causes

1. Mutations in the MTTP gene (microsomal triglyceride transfer protein)
2. Deficiency of ApoB-48 and ApoB-100
3. Impaired lipidation of chylomicrons and VLDL

Pathophysiology

1. Impaired intestinal lipid absorption
2. Reduced VLDL and LDL production
3. Accumulation of lipids in enterocytes and hepatocytes
4. Deficiency of fat-soluble vitamins (A, D, E, K)

Clinical Features

1. Malabsorption and steatorrhea
2. Weight loss and failure to thrive
3. Fatigue and weakness
4. Neurological symptoms (ataxia, neuropathy)
5. Retinitis pigmentosa and visual impairment
6. Acanthocytosis (abnormal RBC morphology)

Diagnosis

1. Laboratory tests:
Low triglycerides and cholesterol
Absence of ApoB-48 and ApoB-100
Elevated liver enzymes
2. Genetic testing (MTTP gene mutation analysis)
3. Imaging studies (MRI, CT scans)

Treatment

1. Dietary modifications:
High-fat diet with medium-chain triglycerides
Fat-soluble vitamin supplements
2. Medications:
Vitamin A and D analogs
Omega-3 fatty acid supplements
3. Supportive care:
Nutritional counseling
Physical therapy

Complications

1. Malnutrition and growth retardation
2. Liver disease and fibrosis
3. Cardiovascular disease
4. Visual impairment and blindness
5. Neurological degeneration

Genetics

1. Autosomal recessive inheritance
2. Mutations in MTTP gene (chromosome 4q23)
3. Genetic counseling

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