TNF and psoriasis: The tumor necrosis factor alpha (TNF-α) is an inflammatory cytokine that is involved in AA pathogenesis and several autoimmune inflammatory disorders like psoriasis and systemic lupus erythematosus, for which the level of this cytokine is found to be relevant with the disease severity and activity, while in AA, only a few studies have measured the level of TNF-α, and the results were controversial [7].