A 61-year-old woman was referred to our department with a 11-year-erythra. In the anterior tibia of both lower extremities, we could see large dark red infiltrating erythema, waxy luster, clear boundary, slight central atrophy, depression and capillary dilatation. He was diagnosed with “dermatitis contusiformis” in local hospitals;, but the treatment of traditional Chinese medicine and external drugs was not effective. She had normal laboratory findings for blood routine test, biochemical indexes, C reactive protein(CRP) and erythrocyte sedimentation rate(ESR).Furthermore, autoimmune antibodies were all negative. The skin pathology showed degeneration and necrosis of collagen fibers, chronic granulomatous inflammation in the dermis, and there were more acute and chronic inflammatory cell infiltration around the small vessels and in the wall of the tube. We eventually diagnosed it as necrobiosis lipoidica (NL) according to the history, erythra morphology and skin pathology. After treatment of low dose hormone and thalidomide for 1 year, the color and range of skin lesions gradually alleviated. NL was a rare chronic granulomatous inflammatory disease. There appeared to be a predominance in females. The incidence of NL was higher in patients with diabetes mellitus, although this asscoiation was currently questioned. NL might also be connected with autoimmune diseases, such as rheumatoid arthritis, sarcoidosis, ulcerative colitis and Crohn’s disease. The pathological changes of the tissue were mainly in the dermis;, including necrotic type, granulomatous type or mixed type. NL typically presented on the pretibial surface of lower extremities. Less typical locations included the face, scalp, vulva and upper limbs. Leisions usually began with small papules and nodules that gradually infiltrated into brown-yellow patches and developed central wax-like atrophy. The diagnosis is often based on clinical examination and skin biopsy. NL is rare and easy to be misdiagnosed. For rheumatologists, we should carefully compare with the nodular erythema, the microscopic polyangitis and allergic purpura. It is significant for differential diagnosis to perform skin biopsy. Lacking of randomized controlled trials, no specific treatment has proven to be the gold standard. First-line therapy mainly consists of intralesional and systemic corticosteriods. Additionally, other reported treatment options include immunomodulator, biological agent, antiplatelet aggregation drug and platelet-rich plasma. These patients need long term follow up continuously for progression of the disease, ulcerations, and possibility of malignant tranformation.