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# Abetalipoproteinemia (Bassen–Kornzweig syndrome)

A rare inherited disorder in which ApoB lipoproteins cannot form; fat and fat-soluble vitamins are poorly absorbed.

Updated 2026-11-01

## Structures involved

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- [Jejunum](https://durgical.com/en/anatomy/jejunum/)
- [Duodenum](https://durgical.com/en/anatomy/duodenum/)
- [Liver](https://durgical.com/en/anatomy/liver/)
- [Ileum](https://durgical.com/en/anatomy/ileum/)
- [Retina](https://durgical.com/en/anatomy/retina/)
- [Cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/)
- [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/)

## In biochemistry

- [Apolipoprotein B (ApoB-100 and ApoB-48)](https://durgical.com/en/biochemistry/enzymes/apolipoprotein-b/)
- [Lipoprotein metabolism](https://durgical.com/en/biochemistry/topics/lipoprotein-metabolism/)
- [Chylomicron](https://durgical.com/en/biochemistry/topics/chylomicron/)

## In physiology

- [Fat digestion and absorption](https://durgical.com/en/physiology/fat-digestion-and-absorption/)
- [Patterns of malabsorption](https://durgical.com/en/physiology/patterns-of-malabsorption/)

## What it is

An autosomal recessive disorder caused by lack of microsomal triglyceride transfer protein (MTP), which prevents chylomicron and VLDL formation.

## Who gets it

Rare: just over 100 cases have been described worldwide. It is suspected in infants with fat malabsorption and very low cholesterol.

## Causes

- Two MTTP gene variants
- Autosomal recessive inheritance

## Risk factors

- Carrier parents
- Related parents

## Pathophysiology

Without MTP, ApoB gets no lipid and is degraded: no chylomicrons leave the gut and no VLDL leaves the liver. Fat is trapped in enterocytes (steatorrhoea) and the liver fills with fat. Blood lacks LDL, triglycerides and fat-soluble vitamins; vitamin E deficiency damages retina and [spinal cord](https://durgical.com/en/anatomy/spinal-cord/), and red cells become spiky (acanthocytes).

## Symptoms and signs

- Fatty diarrhoea (steatorrhoea) and bloating from infancy
- Failure to thrive
- Ataxia, loss of reflexes and of deep sensation
- Progressive vision loss (pigmentary retinopathy)
- Fatty liver

## Red flags

- Infant with steatorrhoea who does not gain weight
- Progressive gait or vision problems
- Bleeding from vitamin K deficiency

## Diagnosis

**Clinical**
Fat malabsorption in an infant with very low cholesterol and triglycerides; later, ataxia and retinopathy.

**Tests**
Very low total cholesterol, nearly undetectable triglycerides, absent ApoB, acanthocytes on the smear, vitamin A, E and K levels, prothrombin time and MTTP genetic testing; duodenal biopsy shows fat-laden enterocytes.

**Imaging**
Abdominal ultrasound for fatty [liver](https://durgical.com/en/anatomy/liver/); fundus examination and optical coherence tomography of the [retina](https://durgical.com/en/anatomy/retina/).

## Treatment

**Lifestyle**
Diet low in long-chain fat, with medium-chain triglycerides under supervision

**Medical**
Supplements of vitamin E, the most important, and of vitamins A, D and K

**Follow-up**
Neurological, eye and liver follow-up

## Complications

- Blindness from retinopathy
- Progressive neuropathy and ataxia
- Hepatic steatosis and fibrosis
- Coagulopathy from vitamin K deficiency

## Prognosis

Starting vitamin E early can prevent or slow nerve and retinal damage.

## Test yourself

Think of the answer, then tap the question to see it.

## Which protein is missing in abetalipoproteinaemia?

MTP (microsomal triglyceride transfer protein), which loads lipid onto ApoB.

## What shape are the red cells in this disease?

Acanthocytes: spiky cells caused by altered membranes.

## Which vitamin is key to preventing nerve damage?

Vitamin E, which cannot reach the tissues without lipoproteins.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Abetalipoproteinemia: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/abetalipoproteinemia/) (MedlinePlus, US National Library of Medicine, 2026); [Bassen-Kornzweig syndrome: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001666.htm) (MedlinePlus, US National Library of Medicine, 2026); [MTTP gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/mttp/) (MedlinePlus, US National Library of Medicine, 2026).

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Source: https://durgical.com/en/conditions/abetalipoproteinemia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/abetalipoproteinemia/