Necrobiosis lipoidica is a rare chronic granulomatous disease, often associated with diabetes mellitus. It is due to collagen degeneration with risk of ulceration. Necrobiosis lipoidica affects 0.3 to 1.2% of diabetic patients, mainly in the leg. Its etiology is not yet well understood. The diagnosis is usually made clinically but a skin biopsy may be necessary in case of atypical lesions. The evolution is chronic with ulceration and degeneration into squamous cell carcinoma as the main complications, which remains exceptional. Several therapies have been proposed: topical corticosteroids in the first instance, but no treatment has proven to have a lasting effective response. Diabetes control does not seem to influence the evolution of the disease.