TNF and oral lichen planus: Genetic polymorphisms of several cytokines have been postulated to be associated with the clinical presentation of OLP.23 It has been reported that genetic polymorphisms of the first intron of the promoter gene of interferon-gamma (IFN-γ ) may be an important risk factor for developing OLP,3,4,13 whereas an increase in the frequency of the 308A tumour necrosis factor-alpha (TNF-α) allele may contribute to the development of additional skin involvement.4 In recent years, it has been reported that OLP is closely related to HLA-DR1.