RESUMEN
Patients affected with congenital nephrogenic diabetes insipidus (CNDI) have reduced ability to concentrate urine. Early diagnosis of CNDI is important to avoid recurrent episodes of severe dehydration. We present a Danish male suffering from typical symptoms and diagnosed with CNDI at the age of 7 months. Gene sequencing of this proband and his mother revealed a novel variant in the gene encoding the antidiuretic hormone receptor (AVPR2). The variant is a deletion of nucleotide c.151 in exon 2 of AVPR2 (GenBank NM_000054.4:c.151del). This 1bp deletion is predicted to cause a frameshift that results in tryptophan replacing valine at position 51 in AVPR2 and a premature stop codon three codons downstream (p.Val51Trpfs*3) likely resulting in faulty expression of the receptor. Identification of disease-causing variants such as the one described here contributes to precise diagnosis, especially in carriers and newborns, thus preventing the long-term physical and intellectual disability observed in some CNDI-patients.