[Syndromes of severe insulin resistance]

The syndromes of extreme severe insulin resistance are mainly caused by genetic defects of the insulin receptor gene (Type A syndrome, Leprechaunism, and Rabson-Mendenhall syndrome) or by the presence of circulating autoantibodies that disrupt the normal functions of the insulin receptor (Type B syndrome). These syndromes are characterized by the hyperinsulinemia and severe insulin resistance and in most cases accompanied by impaired glucose tolerance and diabetes mellitus. The clinical features common to these syndromes are acanthosis nigricans, hyperandrogenism and ovarian dysfunction. On the other hand, an important distinguishing typical feature in type B syndrome is evidence of other autoimmune disorders. [These syndromes can be a contributory causes of insulin resistance in a subpopulation with NIDDM.]