Necrobiosis lipoidica is a rare granulomatous dermatosis, we report observation a of 17-year-old patient, with any pathological history, has presented erythematous oval plaques with an atrophic yellowish center at the anterior surfaces of legs. The diagnosis of necrobiosis lipoidica was confirmed after biopsy. In view of this situation, additional tests were requested. They revealed an unknown diabetes. The anti-GAD antibodies and anti-IA2 antibodies were positive and the patient was placed on insulin therapy. The evolution was marked by a spontaneous regression of lesions.