Abstract. Skin rashes are infrequently encountered in the intensive care units, either as a result or as a cause of admission. The entities of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) form a spectrum of desquamating skin diseases that have multiple etiologies, the most common being drug-related reactions; very rarely, the cause may be cutaneous malignancies. We herein present a unique case of a 54-year-old male patient with psoriasis treated with methotrexate, who presented with a cellulitis-like clinical picture, then developed a severe progressive systemic inflammatory response syndrome, and progressed clinically to SJS, then TEN even after discontinuing the antibiotics and methotrexate. A skin biopsy demonstrated an aggressive and rapidly-progressing T-cell lymphoma. The present case highlights the necessity of skin biopsy when encountering SJS and TEN in the ICU in order to identify potentially treatable/controllable causes. Although it appeared reasonable to correlate TEN solely to medications, the skin biopsies clearly demonstrated an aggressive T-cell skin lymphoma. In a patient with a better general condition it may have been helpful to treat this malignancy. TEN is a life-threatening condition and skin biopsy is the cornerstone of diagnosis, despite the presence of multiple risk factors and the typical physical findings of a drug-induced reaction.