The familial forms of the disorder are very rare. It may be inherited as a dominant or recessive trait in patients with the isolated vasopressin deficiency. These patients become obviously polyuric in the first year or two of life. Plasma vasopressin is undetectable under basal conditions, but it may be released following profound osmotic stimulation. The polyuria in patients with the DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and [nerve] deafness) syndrome is less profound than in those with the isolated defect. No specific cause can be found for some fifty per cent of patients with acquired cranial diabetes insipidus, although approximately one-third of these patients may have circulating antibodies to the vasopressin- synthesising neurone, thus suggesting an autoimmune aetiology.
