Nephrogenic Syndrome of Inappropriate Antidiuresis (NSIAD) was first described in 2005 in a report of two infants with symptomatic hyponatremia caused by gain-of-function variants in the arginine vasopressin (AVP) receptor 2 (AVPR2) gene (MIM *300538) (Feldman et al. 2005). This rare genetic disorder is characterized by hyponatremia, hypoosmolality, euvolemia, inappropriately concentrated urine, increased natriuresis, and undetectable or very low circulating levels of AVP, also known as antidiuretic hormone (ADH). The condition results from gain-of-function mutations in the AVPR2 gene, which lead to the constitutive activation of the receptor (Feldman et al. 2005; Levtchenko and Monnens 2010; Erdélyi et al. 2015).