Slowly progressive insulin-dependent diabetes mellitus in an elderly patient with Graves' disease.

We report a case of slowly progressive insulin-dependent diabetes mellitus in an elderly patient with Graves' disease. A 69-year-old man presented with apathetic thyrotoxicosis and weight loss. Laboratory findings indicated insulin-dependent diabetes mellitus (IDDM) with Graves' disease. Human leukocyte antigens DR4 and DR9, which are recognized as markers for IDDM with autoimmune thyroid disease, were detected. The clinical course of the IDDM was compatible with the slowly progressive type. Onset of this disease during old age is rare, and such cases should be analyzed with a thyroid function test because the symptom of thyrotoxicosis may be masked in the elderly.