Dermatological problems occur with increased frequency in individuals with diabetes mellitus (DM). Cutaneous manifestations may be the first presenting sign of DM or even precede the diagnosis by many years. The main changes in the skin are due to alterations of microcirculation, the nervous system, and collagen. The most common skin problems in DM are acanthosis nigricans, necrobiosis lipoidica, diabetic dermopathy, scleredema, and granuloma anulare. The purpose of this review is to describe the molecular and anatomopathological alterations occurring at the skin during DM, and to illustrate the most important and common clinical skin manifestations in patients with DM. .