In contrast to our hypothesis, ME/CFS samples were negative for autoantibodies against PDC, with the exception of three ME/CFS patients: #43 (A = 1.217 at 1:500); ME/CFS patient #69 (A = 0.406 at 1:500); ME/CFS patient #166 (A = 0.418 at 1:500); and #21, a ME/CFS patient with FM comorbidity (A =1.658 at 1:500) that was found weakly/intermediately positive. Here, PDC is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.