BackgroundThe relationship between compromised immune system and the development of malignancy, generalized dermatitis, and infection after sulfur mustard gas exposure has been established.Main observation:We introduce a 58-year-old man with an abrupt, de novo and erythrodermic eruption in 2002 that was previously exposed to sulfur mustard during the Iran - Iraq war in 1987. Six weeks after the onset of diffuse eruption, he developed papules on the glans penis and generalized dermatophytosis. A biopsy of his eruption was consistent with cutaneous T-cell lymphoma/Sézary syndrome. A complete blood count demonstrated leukocytosis, eosinophilia and atypical lymphocytosis. Subsequently, Sézary syndrome was confirmed and T-cell count with increased CD4/CD8 in flow cytometry. The biopsy of his penile papules was consistent with Kaposi's sarcoma.Conclusion:These findings suggest a causative relationship between sulfur mustard gas exposure, cutaneous T cell lymphoma and immune compromised state with opportunistic infections.