Antibodies against the insulin receptor in paraneoplastic acanthosis nigricans.

Acanthosis nigricans is a skin disorder associated with endocrine abnormalities, autoimmune disease, and systemic malignancies. Insulin resistance is a common accompaniment of the nonmalignant varieties of acanthosis nigricans. A 44-year-old man is described with a functioning metastatic pheochromocytoma, acanthosis nigricans, and insulin-resistant diabetes mellitus. Studies of insulin action showed a low titer of anti-insulin antibodies and a very high titer of antibodies against the insulin receptor. This case documents for the first time insulin resistance due to anti-insulin receptor antibodies in a paraneoplastic variety of acanthosis nigricans.