Previous studies have reported a link between PPD symptoms and single nucleotide polymorphisms (SNPs) at several genes, such as 5-HTT, Catechol-O-methyl transferase (COMT), Monoamine Oxidase (MAO)11, Brain-Derived Neurotrophic Factor (BDNF)12 and Cytochrome P450 Family 2 Subfamily D Member 6 (CYP2D6)13. Here, CYP2D6 is linked to progressive pseudorheumatoid arthropathy of childhood.