Growth retardation in untreated autosomal dominant familial neurohypophyseal diabetes insipidus caused by one recurring and two novel mutations in the vasopressin-neurophysin II gene.

OBJECTIVE

Autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI), a disorder caused by mutations in the vasopressin (AVP)-neurophysin II (NPII) gene, manifests gradually during early childhood with progressive polyuria and polydipsia. Patients are usually treated with synthetic AVP analog. If unlimited access to water is provided, prognosis is usually good even in the absence of specific treatment. In this study, we describe three families with adFNDI, in which growth failure was a prominent complaint, on the clinical and molecular level.

DESIGN/METHODS: Histories from affected and unaffected family members were taken. Height and weight of index patients were recorded longitudinally. Patients underwent water deprivation tests, magnetic resonance imaging, and genetic analysis. One mutant was studied by heterologous expression in cell culture.

RESULTS

A total of ten affected individuals were studied. In two of the three pedigrees, a novel mutation in the AVP-NPII gene was found. The index children in each pedigree showed growth retardation, which was the reason for referral in two. In these cases, water intake was tightly restricted by the parents in an attempt to overcome suspected psychogenic polydipsia and to improve appetite. Once the children were treated by hormone replacement, they rapidly caught up to normal weight and height.

CONCLUSIONS

Genetic testing and appropriate parent counseling should be enforced in adFNDI families to ensure adequate treatment and avoid chronic water deprivation, which causes failure to thrive.