Two cases of hereditary diabetes insipidus (DI) are described, with an autopsy finding in one. The patients were brothers and 7 other relatives had symptoms of DI. The transmission of the disease in this family seemed to be an autosomal dominant trait with incomplete penetration. Both patients had the incomplete type of DI, which is diagnosed by the response of plasma AVP and the change in Uosm/Posm to 14 h water deprivation. The post-mortem examination in Case 1 showed that there was no atrophy of the supraoptic nucleus and paraventricular nucleus, but immunohistochemical studies revealed, that the paraventricular nucleus scarcely had any vasopressin positive cells in contrast to an autopsy control.

This finding suggests that there may be a congenital defect in AVP synthesis in some cases of hereditary DI.