Insulin-resistant diabetes with insulin receptor autoantibodies in a male patient without acanghosis nigricans.

A 51-yr-old, nonobese, male patient presented with hyperglycemia and a recent 40-pound weight loss. Severe insulin resistance was documented in studies in which high amounts of insulin were infused using the Biostator GCIIS. Diabetic control was finally achieved with subcutaneous injections of 470 U of insulin per day. Positive laboratory findings included a mild pancytopenia, elevated erythrocyte sedimentation rate, decreased C3 and properdin, and increased IgA. Antinuclear or other autoantibodies were not present. Insulin antibody levels were within the range usually present in insulin-treated diabetic patients. Acanthosis nigricans was not present. Incubation of the patient's serum with IM-9 lymphoblastoid cells revealed that an insulin receptor antibody was present in a serum dilution of 1:80. Insulin-resistant diabetes mediated by insulin receptor antibodies may present in patients with immunologic findings but without overt dermatologic stigmata.