Mucormycosis is an invasive infection caused by opportunistic fungi. Rhizopus, Lichtheimia, Mucor and Rhizomucor are the most common isolated genera. Primary cutaneous mucormycosis is usually related to traumatic injuries, but immunocompromised cases are associated with underlying conditions such as diabetes mellitus and malignancies. The treatment of choice is surgical debridement and liposomal amphotericin B. We present a 40-year-old male with fever and a painful necrotic lesion on the middle back and history of poorly controlled diabetes mellitus. Rhizopus oryzae was isolated and identified using an internal transcribed spacer regions ITS1 and ITS2. An initial good response to treatment was observed; however, 7 days later a diabetic ketoacidosis due to poor adherence to treatment caused a lethal outcome.