While CARD15 defects confer susceptibility Crohn's disease, Blau syndrome, and psoriatic arthritis [7] no such defects were found in patients with sarcoidosis [13], ankylosing spondylitis [14] Wegener's granulomatosis [15], systemic lupus erythematosus [16], or rheumatoid arthritis [17]. Here, NOD2 is linked to psoriatic arthritis.