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GTR Home > Conditions/Phenotypes > Methylcrotonyl-CoA carboxylase deficiency


An inherited disorder of leucine metabolism with characteristics of a highly variable clinical picture ranging from metabolic crisis in infancy to asymptomatic adults. Patients have a variable clinical phenotype with the vast majority of patients being asymptomatic and a small subgroup displaying symptoms of an organic aciduria, usually in association with environmental triggering factors. This disease is due to mutations in the MCCC1 (3q27.1) or MCCC2 (5q12-q13) genes. Mutations in these genes lead to reduced or absent 3-MCC activity, thereby allowing the toxic byproducts of leucine processing to build up and cause clinical symptoms. Inherited autosomal recessively. [from SNOMEDCT_US]

Genes See tests for all associated and related genes

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Practice guidelines

  • ACMG ACT, 2022
    American College of Medical Genetics and Genomics, Newborn Screening ACT Sheet, Elevated C5-OH Acylcarnitine, Organic Acidemias, 2022
  • ACMG Algorithm, 2022
    American College of Medical Genetics and Genomics, Algorithm, Organic Acidemias: Elevated C5-OH, 2022

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