ABSTRACT
Purpose The causes of hereditary nephrogenic diabetes insipidus (HNDI) are the mutations in the arginine vasopressin V2 receptor gene (AVPR2) (90%) and aquaporin 2 gene (AQP2) (10%). Although it is possible to perform mutation analysis where available, differentional diagnosis at clinical bases remains valuable. Methods In this report we present two cases of HNDI diagnosed at clinical bases with a desmopressin infusion test as AQP2 gene mutations. The results were verified by genetic analysis to stress that a desmopressin infusion test is valuable for differential diagnosis of HNDI. Results With a desmopressin infusion test, factor VIII levels were increased up to 219% and 214% respectively, establishing the presence of V2 receptor. With direct sequencing of the AQP2 gene, a previously described splicing mutation in a new codon (380) and a new frameshift mutation were determined in case 1 and case 2 respectively. Conclusion It is concluded that the desmopressin infusion test is a simple and reliable method for the diagnosis and differential diagnosis of HNDI in early childhood.