Exclusions include “(a) psoriasis or a history of psoriasis in the patient or a first-degree relative, (b) arthritis in an HLA-B27 positive male beginning after the 6th birthday, (c) ankylosing spondylitis, enthesitis-related arthritis, sacroiliitis with inflammatory bowel disease, Reiter's syndrome, or acute anterior uveitis, or a history of one of these disorders in a first-degree relative, (d) the presence of IgM rheumatoid factor on at least 2 occasions at least 3 months apart” [3]. This evidence concerns the gene CD40LG and psoriasis.