XMRV, originally identified in RNase L–deficient patients with familial prostate cancer, has gained interest since recent work showed its protein expression in as many as 23% of prostate cancer cases (10) and XMRV-specific sequences were detected in PBMCs of 67% patients with chronic fatigue syndrome (5). Here, RNASEL is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.