Although it was a single-arm, nonrandomized trial with a small sample size (n = 20) of mostly adults, it provides data showing that abatacept is a safe drug (five serious infections, none lasting > 3 months, and no EBV/CMV viremia-based events were reported), and that the CTLA4 haploinsufficiency (CHAI) morbidity score in most organ systems either remained stable or improved. Here, CTLA4 is linked to infection.