Variants listed in the table have been provided by the authors. GeneReviews staff have not independently verified the classification of variants.

GeneReviews follows the standard naming conventions of the Human Genome Variation Society (varnomen​.hgvs.org). See Quick Reference for an explanation of nomenclature.

See cbs​.lf1.cuni.cz for an updated list of PCCB pathogenic variants and polymorphisms.

Variant designation that does not conform to current naming conventions

Common in Japan [Yang et al 2004]

Common in Spanish populations [Desviat et al 2004]

Most frequent mutated allele reported in individuals of northern European origin (~30%)

Detected in asymptomatic newborns through newborn screening in Japan; long-term effects are yet to be determined [Yorifuji et al 2002].

Common pathogenic variant among Inuits in Greenland with a carrier frequency in that community of ~5% [Ravn et al 2000]

A less severe form of PA is seen in some Amish and Mennonite communities.