PRTN3 and post-transplant lymphoproliferative disease: RF was positive in 3.8% (five of 131), and ACPA was positive in 4.8% (seven of 147) at least at one time point. A total of 7.2% (12 of 167) patients were found to have a positive RF or ACPA test at least at one time point. There was no difference in the proportion of patients with RF and/or ACPA based on the initial presenting manifestations of their LD, nor the symptoms of PTLD at later evaluation; however, the small sample size may limit our ability to detect these clinical differences.