Severe hypoglycemia due to insulin autoimmune syndrome with autoantibodiescrossreactive to proinsulin

We report the case of a 69-year-old woman with insulin autoimmune syndrome first misdiagnosed as insulinoma. The case demonstrates the difficulties to correctly diagnose this rare disorder as both insulin and proinsulin level s were increased by crossreactive autoantibodies. No known triggering agent could be identified. We suggest that this diagnosis should be considered m ore often also in caucasian patients to avoid useless operations for such p atients.