A novel mutation in AVPR2 causing congenital nephrogenic diabetes insipidus with complete resistance to antidiuretic hormone.

A 6-month-old male infant presented with failure to thrive. Hypernatraemia and elevated serum osmolality in the presence of low urine sodium and osmolality led to the diagnosis of diabetes insipidus. Administration of 1-deamino-8-D-arginine vasopressin (dDAVP) neither decreased urine volume nor increased urine osmolality indicating congenital nephrogenic diabetes insipidus. Molecular analysis in the arginine-vasopressin receptor-2 gene (AVPR2) located on chromosome Xq28 demonstrated a novel 5-base pair deletion (c.962-966delACCCC; g.1429-1433delACCCC) leading to a shift of the reading frame (p.Asn321fs) and a premature termination codon implying an absent or non-functional protein. Treatment with hydrochlorothiazide, amiloride and indomethacin led to a favourable clinical course.