VDR and vitamin D deficiency: Vitamin D has a physiological role in maintenance of innate and acquired immunity as vitamin D receptors are present in primary lymphoid organs.10 It has modulatory effect on cells of immune system and decreases levels of proinflammatory cytokines.11 In vitro studies have shown vitamin D deficiency causes inflammation by modulating action of helper T cells and regulatory T cells.12 Vitamin D supplementation is found to have significant improvement in fatigue in otherwise healthy persons with vitamin D deficiency and also in patients with established RA.13