Mexican beer dermatitis: a unique variant of lime phytophotodermatitis attributable to contemporary beer-drinking practices.

environmental triggers. It is inherited as an autosomal trait and may be triggered by stimuli including sunlight and artificial UV light, viral infections, immunosuppressive conditions (hematologic malignancies, organ transplant, or autoimmune disease), and immunosuppressant therapies. The role of immunosuppressant therapy is supported by the observation in at least 1 case report of remission of DSP on withdrawal of immunosuppressant therapy. To our knowledge, there are no reports of DSP arising in patients receiving etanercept, other tumor necrosis factor (TNF) antagonists, or biological agents of other classes. The mechanism by which immunosuppressant therapy induces DSP is not clear. It may cause the phenotypic expression of the disease in a genetically predisposed patient to manifest by either directly triggering the expression of abnormal clones of epidermal cells or by disrupting the growth of the epidermis and promoting clonal cell proliferation. Alternatively, immunosuppressant therapy might reduce immune surveillance and allow the proliferation of the abnormal clones. This theory is supported by the observation that T cells are important in the prevention of porokeratotic clonal growth. Etanercept is a recombinant TNF receptor fusion protein that binds to and inhibits TNF. Tumor necrosis factor is important in inflammatory, apoptotic, and cellular proliferation pathways. Etanercept, by inhibiting TNF, results in a decrease in the number of T cells, which are important in immune surveillance and in preventing the abnormal keratinocyte clonal proliferation that occurs in DSP. This case is of interest because DSP was noted after etanercept treatment was introduced, and we suggest that the immunosuppressant effects of etanercept contributed to DSP development. As more patients are treated with biological immunosuppressant therapy, DSP may become more frequently reported as a common adverse effect of these therapies.