Dysregulation in toxins efflux may impair xenobiotic metabolism, which potentially may be associated with ME/CFS pathogenesis [206] via targeting the xenobiotic receptors CAR (constitutive active/androstane receptor) [207], PXR (Pregnane X receptor) [208], LXR (The liver X receptor), FXR (The farnesoid X receptor) [209, 210], VDR (Vitamin D receptor) and AHR (aryl hydrocarbon) cascades [211–213]. The gene discussed is VDR; the disease is myalgic encephalomeyelitis/chronic fatigue syndrome.