Also, increased PAD2 and PAD4 levels, as well as H3 citrullination/deimination were identified in post-mortem prefrontal cortex of patients with X-linked Dystonia Parkinsonism [26]; albeit other PAD isoforms were not assessed in that study, contrary to our current study where all five PADs were assessed in post-mortem PD brains. The gene discussed is PADI4; the disease is X-linked dystonia-parkinsonism.