Chronic activation of NFκB is hypothesised to occur in CFS/ME/SEID (see Fig. 1); in 2011, Hoeck and Pall suggested that vitamin D3 (1,25(OH)2D3) supplementation may be helpful in this disease owing to the ability of active vitamin D3 to repress activation of NFκB, via binding to vitamin D receptor [23]. Here, NFKB1 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.