Skin-related complications of insulin therapy: epidemiology and emerging management strategies

The incidence and prevalence of all types of diabetes mellitus is increasing at an alarming rate. Modern therapy involves greater and earlier use of intensive insulin regimens in order to achieve better control of blood glucose levels and reduce the long-term risks associated with the condition. Insulin therapy is associated with important cutaneous adverse effects, which can affect insulin absorption kinetics causing glycemic excursions above and below target levels for blood glucose. Common complications of subcutaneous insulin injection include lipoatrophy and lipohypertrophy. The development of lipoatrophy may have an immunological basis, predisposed by lipolytic components of certain insulins. Repeated use of the same injection site increases the risk of lipoatrophy--with time, patients learn that these areas are relatively pain free and continue to use them. However, the absorption of insulin from lipoatrophic areas is erratic leading to frequent difficulties in achieving ideal blood glucose control. With the increasing use of modified, rapidly absorbed analog insulins (e.g. insulin lispro, insulin aspart) the incidence of lipoatrophy occurring has decreased over recent years. The likelihood of lipoatrophy can be reduced by regular rotation of injection sites but once developed, practical benefits may be obtained by insulin injection into the edge of the area, co-administration of dexamethasone with insulin, or changing the mode of insulin delivery. Lipohypertrophy is the most common cutaneous complication of insulin therapy. Newer insulins have also reduced its prevalence considerably, although its adverse effect on diabetic control is similar to lipoatrophy through impaired absorption of insulin into the systemic circulation. Experience with liposuction at these sites is limited, although good cosmetic results have been achieved. Local allergic reactions to insulin are usually erythema, pruritus, and induration. These allergic reactions are usually short-lived, and resolve spontaneously within a few weeks. Useful adjuncts to managing allergic reactions include addition of dexamethasone to the insulin injection, desensitization to insulin, or a change in delivery system utilizing insulin pump therapy or potentially inhaled insulins when these become available. The use of insulin pump therapy in managing cutaneous complications of insulin therapy is increasing, but this method itself carries risks of abscess formation and scarring. Fortunately, with improved education of patients these are relatively uncommon. Although many of the cutaneous manifestations are decreasing with the use of newer insulins, they may still influence glycemic control and increase the risk of hypoglycemia as well as have a cosmetic impact on a patient. The introduction of novel therapies and newer delivery systems is likely to reduce the cutaneous problems associated with long-term insulin use.