GastroenterologyTier 2Disease (DEADMAN)

Abetalipoproteinaemia

Description

A rare autosomal recessive disorder of microsomal triglyceride transfer protein (MTP) deficiency, preventing assembly/secretion of chylomicrons and VLDL - resulting in severe fat malabsorption and the near-total absence of apolipoprotein B-containing lipoproteins from plasma

Very rare, typically presenting in infancy with failure to thrive and steatorrhoea

MTP is required to load triglycerides onto apolipoprotein B within enterocytes (forming chylomicrons) and hepatocytes (forming VLDL) - its absence traps triglyceride within these cells, preventing dietary fat and fat-soluble vitamin absorption/transport, and secondarily causing the fat-soluble vitamin (A, D, E, K) deficiencies that drive much of the clinical picture

Infancy: failure to thrive, steatorrhoea, abdominal distension
Progressive complications from fat-soluble vitamin deficiency: vitamin E deficiency causes a progressive spinocerebellar degeneration (ataxia, areflexia, proprioceptive loss - the most clinically significant long-term complication) and retinitis pigmentosa (vitamin A/E related)
Acanthocytosis (spiky, irregular red cells) on blood film is a characteristic finding, from altered red cell membrane lipid composition
Fasting lipid profile shows near-absent LDL/VLDL/chylomicrons with very low total cholesterol and triglycerides - a distinctive, essentially diagnostic pattern

High-dose fat-soluble vitamin supplementation (particularly vitamin E, at doses far exceeding standard supplementation, given the absorption defect) is the cornerstone of management, aimed specifically at preventing/slowing the neurological complications
Dietary fat restriction with medium-chain triglyceride (MCT) supplementation - MCTs are absorbed directly into the portal circulation without requiring chylomicron formation, bypassing the defective pathway
Regular neurological and ophthalmological monitoring given the progressive nature of untreated vitamin E-deficiency complications

Vitamin E deficiency neurological syndrome, retinitis pigmentosa, acanthocytosis, fat-soluble vitamin deficiency generally

Early diagnosis and aggressive vitamin E supplementation can prevent or substantially slow the progressive neurological complications - delayed diagnosis allows irreversible neurodegeneration to develop, making early recognition (from the failure to thrive/steatorrhoea/characteristic lipid profile combination) clinically important

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