CTLA4 and rheumatoid arthritis: Abatacept, a CTLA4 fusion protein, was approved for use in rheumatoid arthritis in 2008 (5 years before the approval of ipilimumab67) and, following this, has subsequently demonstrated efficacy in many diverse IMRDs including psoriatic arthritis, juvenile idiopathic arthritis (JIA), myositis,68 giant cell arteritis (GCA)69 and ANCA vasculitis.70