Granulomatous slack skin is an extremely rare cutaneous T-cell lymphoma, which often pursues an indolent disease course. Clinically, it is characterized by areas of redundant and lax skin in flexural areas, with variable erythema. Histologic findings include granulomatous T-cell infiltrates with loss of elastic fibers and poikilodermic change. In this article, we report a patient with unusual rapidly progressive ulcerative and gangrenous skin lesions, leading to amputation and ultimately demise. We also review the literature on granulomatous slack skin with similarly aggressive clinical course and discuss the differential diagnosis.