The authors further concluded that CYP26B1, but not CYP26A1, is the main post-natal enzyme clearing all-trans-retinoic acid, which coincides well with our results showing that many SNPs in CYP26B1 (but not CYP26A1) display differences (under- or over-representation) in GPD vs. GUN and thus in the manifestation of PD. The gene discussed is CYP26A1; the disease is Parkinson disease.