JMY Ma, LCN Chan, SC Chong, HM Cheung

Abstract

A 7-month-old male infant presented with repeated vomiting and failure to thrive. Hypernatraemia, high serum osmolality, low urine osmolality, and lack of response to DDAVP, suggested diagnosis of nephrogenic diabetes insipidus. Genetic exome sequencing showed a novel hemizygous c.802_834dup, p.(Lys268_Val278dup) variant in exon 3 of AVPR2 gene, with in-frame duplication of 11 residues starting from 268th codon (NM_000054.6). This variant is of uncertain significance; the clinical phenotype was compatible with nephrogenic diabetes insipidus. Treatment with indomethacin, hydrochlorothiazide led to good clinical outcome.