Lupus mesenteric vasculitis is one of the most devastating complications of systemic lupus erythematosus (SLE) and may lead to a spectrum of complications, including ulceration, haemorrhage, bowel necrosis, perforation, serositis and ascites. Among such complications, intestinal necrosis and intestinal perforation are the most serious. Rectal necrosis is a rare manifestation of SLE, with only two case reports in the English literature. Here, we report the case of a 59-year-old male patient with SLE complicated by rectal necrosis that was initially misdiagnosed as acne and rectal tumours. After two surgeries and the addition of immunosuppressive therapy, the patient was eventually cured and discharged.