This is the first such study evaluating any linkage between the BRCA1 gene (predisposing to breast and ovarian cancer), CHEK2 gene (cancers of the prostate, thyroid, breast, colon, stomach), MC1R gene (melanoma, non-melanoma skin cancers), ATM gene (cancers of the breast, pancreas, thyroid) and the XPD gene (melanoma, oesophageal squamous cell carcinoma, cancers of the lung and breast) with psoriasis. This evidence concerns the gene ATM and prostate cancer.