Further, there were no significant differences in the baseline serum BAFF levels between patients with mild, moderate or severe ME/CFS according to the NICE-guidelines [25], or between baseline serum BAFF levels and disease duration categorized as 2–5, 5–10 and >10 years (data not shown). Here, TNFSF13B is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.