SummaryBackgroundLarge leg ulcers (LLU) may complicate autoimmune diseases. They pose a therapeutic challenge and are often resistant to treatment. To report three cases of autoimmune diseases complicated with LLU.Case ReportCase 1. A 55-year old woman presented with long-standing painful LLU due to mixed connective tissue disease (MCTD). Biopsy from the ulcer edge showed small vessel vasculitis. IV methylprednisolone (MethP) 1 G/day, prednisolone (PR) 1mg/kg, monthly IV cyclophosphamide (CYC), cyclosporine (CyA) 100mg/day, IVIG 125G, ciprofloxacin+IV Iloprost+enoxaparin+aspirin (AAVAA), hyperbaric oxygen therapy (HO), maggot debridement and autologous skin transplantation were performed and the LLU healed. Case 2. A 45-year old women with MCTD developed multiple LLU’s with non-specific inflammation by biopsy. MethP, PR, hydroxychloroquine (HCQ), azathioprine (AZA), CYC, IVIG, AAVAA failed. Treatment for underlying the LLU tibial osteomyelitis and addition of CyA was followed by the LLU healing. Case 3. A 20-year-old man with history of polyarteritis nodosa (PAN) developed painful LLU’s due to small vessel vasculitis (biopsy). MethP, PR 1 mg/kg, CYC, CyA 100 mg/d, AAVAA failed. MRSA sepsis and relapse of systemic PAN developed. IV vancomycin, followed by ciprofloxacin, monthly IVIG (150 g/for 5 days) and infliximab (5 mg/kg) were instituted and the LLU’s healed.ConclusionsLLU are extremely resistant to therapy. Combined use of multiple medications and services are needed for healing of LLU due to autoimmune diseases.