Co-existent diabetes mellitus and diabetes insipidus, a familial disease.

Three male siblings with diabetes mellitus are described, two of whom also had coexistent diabetes insipidus. The co-existence of diabetes mellitus and insipidus appears to represent a single genetic abnormality and may or may not be accompanied by primary optic atrophy. Chlorpropamide was effective in controlling the symptoms of diabetes mellitus and diabetes insipidus.