Patients treated with belatacept (Nulojix, Bristol-Myers-Squibb) are at increased risk of developing 2 potentially fatal complications: post-transplant lymphoproliferative disorder (PTLD), which predominantly involves the central nervous system, and progressive multifocal leukoencephalopathy, according to a recent FDA Safety Alert. The risk of PTLD is higher for transplant patients who have never been exposed to Epstein-Barr virus (EBV) and therefore is indicated for use only in transplant patients who are EBV seropositive.