The Skin and Diabetes Mellitus

The cutaneous signs of diabetes are the manifestations of multiple factors. Abnormal carbohydrate metabolism, other altered metabolic pathways, atherosclerosis, microangiopathy, neurone degeneration, and impaired host mechanisms all play a role. Although some cutaneous reactions are secondary to treatment, skin manifestations may be the first clue to an underlying diabetic diathesis. Plasma glucose concentrations of greater than 140 mg/ dl on more than one occasion are considered diagnostic of diabetes. Diabetics are classified into two welldefined primary groups and a miscellaneous collection of secondary causes. Insulin-dependent diabetes (IDDM, type 1) has an earlier age of onset (juvenile diabetes) with a susceptibility to ketoacidosis. Non-insulindependent diabetics (adult onset, type 2) are more likely to have a family history of diabetes and can demonstrate obesity of the upper trunk. Diabetic diets, weight loss, and oral hypoglyceric agents are more likely to control these patients because insulin levels are not generally as low as those found in type 1 diabetes. Diabetes may develop secondary to altered metabolic states that antagonize insulin, such as steroid hormone therapy, Cushing's disease, or pancreatitis. Rare genetic syndromes associated with secondary diabetes are listed at the end of Table 1 and receptor abnormalities discussed under acanthosis nigricans. A classification of cutaneous manifestations i s listed in Table 1. The more important clinical associations will be discussed individually.