Considering the seriousness of vitamin D deficiency as a public health concern as well as the high prevalence of OLP and the need for an alternative to steroids in its management, together with the immune-modulatory effect of vitamin D that involves down-regulation of pro-inflammatory cytokines such as IFN-γ, we conducted the present study to investigate the role of vitamin D in the management of vitamin D-deficient OLP patients. The gene discussed is IFNG; the disease is vitamin D deficiency.