BackgroundFamilial neurohypophyseal (central) diabetes insipidus (DI) is caused by mutations in the arginine vasopressin–neurophysin II (AVP–NPII) gene. The majority of cases is inherited in an autosomal dominant way. In this study, we present the clinical features of a mother and her son with autosomal dominant neurohypophyseal DI caused by a novel mutation.CaseA thirty-four-year-old woman and her three-year-old son were evaluated because of polyuria and polydipsia since the age of 1.5 years onwards. Both patients were subjected to a water deprivation test confirming the diagnosis of central DI. Magnetic resonance imaging of the brain of the mother showed a hypothalamus without apparent abnormalities and a relatively small neurohypophysis without a hyperintense signal. Mutation analysis showed a c.322G>T (p.?/p.Glu108X) in Exon 2 of the AVP–NPII gene in both mother and son.DiscussionThis study reports neurohypophyseal DI in a mother and her son due to a novel mutation in Exon 2 of the AVP–NPII gene. Clinical and pathophysiological aspects of this disease are shortly reviewed and discussed.