Cytochrome P450 4F22 (CYP4F22) is thought to 20-hydroxylate trioxilin A3 (TrXA3), an intermediary metabolite from the 12(R)-lipoxygenase pathway. This pathway is implicated in proliferative skin diseases. The major products of arachidonic acid in keratinocytes are 12- and 15-HETE which undergo biotransformation to products involved in skin hydration. CYP4F22 mutations can lead to autosomal recessive congenital ichthyosis (ARCI) (Lefevre et al. 2006).