Novel Variant of AVPR2 Giving Rise to X-Linked Congenital Nephrogenic Diabetes Insipidus in a 7-Month-Old Danish Boy

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.