Abstract: Objective　To analyze the clinical characteristics，genetic diagnosis and treatment of congenital nephrogenic diabetes insipidus (CNDI). Methods　Clinical data of two patients diagnosed as diabetes insipidus was retrospectively analyzed. The first patient was a five-year-old boy with a history of polydipsia and polyuria for three years and of growth retardation for half a year. The second patient was first admitted at the age of 3 years and 2 months old with a history of polydipsia and polyuria for two years. Fluid deprivation test and dDAVP intranasal test confirmed both patients had persistent low urine specific gravity. Then peripheral blood samples of two patients and their parents were collected, and genetic test for diabetes insipidus was performed. Two patients were both treated with hydrochlorothiazide combined with indomethacin and therapeutic effect was followed up one year later. Results　Depending on polydipsia, hyperuresis and results of fluid deprivation test and dDAVP intranasal test, CNDI was clinically confirmed. Gene sequencing found a novel c.650C>T hemizygous mutation in the exon 2 of AVPR2 of the first patient, and a novel large deletion included exon 1 and exon 2 region of AVPR2 gene in the patient 2. His mother was a mutation carrier, no mutation was found in his father. Both patients were treated with hydrochlorothiazide and indomethacin for one year. Then follow-up found urine volume and nocturia were reduced and no electrolyte disturbance and renal function damage in two patients. Conclusion　AVPR2 gene was a main disease-causing gene for CNDI. Two variants found in the both patients were not reported. Hydrochlorothiazide and indomethacin can relieve clinical symptom.

Key words: AVPR2 gene;　gene mutation;　congenital nephrogenic diabetes insipidus