A case of pyoderma gangrenosum in a patient with rheumatoid arthritis treated with abatacept

Pyoderma gangrenosum (PG) is a neutrophilic dermatosis induced by trauma or infection, which frequently appears on the lower legs. Various autoimmune diseases and systemic tumour necrosis factor (TNF)-α-blocking treatment cause PG, suggesting that T-cell-mediated reactions are involved in the aetiology. We report here for the first time a case of PG occurring during treatment with abatacept, a T-cell co-stimulation blocker. In addition, we discuss a possible underlying disease mechanism.