Although superoxide production was higher in both patients with severe erythrodermic (EPS) and arthropathic (PSA) forms of psoriasis, increased SOD and CAT levels were found in EPS, and decreased SOD levels were found in arthropathic PSA forms of psoriasis [82], suggesting that only severe forms of psoriasis are associated with decreased enzymatic antioxidant defences. This evidence concerns the gene CAT and psoriasis.