A significant proportion of inflammatory bowel disease (IBD) patients develop skin complications during infliximab or adalimumab therapy. Both drugs are thought to act via induction of apoptosis in activated inflammatory cells.Deoxyribonuclease (DNase) I is endonuclease hydrolyzing double-stranded DNA during apoptosis and its deficiency has been implicated in several autoimmune disorders.Low DNase I activity may be a risk factor for development of immune-mediated skin complications during biological therapy in patients with IBD.