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Congenital bile acid synthesis defect type 4

Synonym(s) 2-methylacyl-CoA racemase deficiency
AMACR deficiency
Alpha-methyl-acyl-CoA racemase deficiency
Liver disease-retinitis pigmentosa-polyneuropathy-epilepsy syndrome
Prevalence <1 / 1 000 000
Inheritance Autosomal recessive
Age of onset All ages
  • K76.8
  • C1858328
  • C535444
MedDRA -


Disease definition

Congenital bile acid synthesis defect type 4 (BAS defect type 4) is an anomaly of bile acid synthesis (see this term) characterized by mild cholestatic liver disease, fat malabsorption and/or neurological disease.


Five cases have been reported to date: two siblings presenting with neonatal cholestasis and three adults with neurological disease.

Clinical description

The clinical presentation of this defect varies. Infants present with severe fat and fat-soluble vitamin deficiencies, hematochezia and mild cholestasis, whereas adults present with various neurological disorders. It is possible that the adults had undocumented mild liver disease and fat-soluble vitamin deficiency in earlier life that led to neurological disease.


BAS defect type 4 is caused by a mutation in the AMACR gene (5p13.2-q11.1).

Diagnostic methods

Diagnosis is based on liquid secondary ionization mass spectrometry (LSIMS), gas chromatography-mass spectrometry (GC-MS) and electrospray ionization-tandem mass spectrometry analysis of urine, serum and bile.

Genetic counseling

Transmission is autosomal recessive.

Management and treatment

Treatment is based on primary bile acid therapy with cholic acid. Dietary restriction of phytanic and pristanic acids is likely to be necessary in the long term to prevent neurotoxicity.

Expert reviewer(s)

  • Pr James HEUBI

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