A Novel Pathogenic Variant of the AVPR2 Gene Leading to Arginine Vasopressin Resistance from the Neonatal Period

Diabetes insipidus (DI) in newborn is an extremely rare condition, simultaneously the age of presentation is a strong suggestion of genetic background of disease. The differ-ential diagnosis should include arginine vasopressin deficiency (AVD) and arginine vasopressin resistance (AVR). Some novel diagnostic tools such as copeptin evaluation and genetic tests are vital for the early diagnosis. Case report: We present the case of a 1-month-old boy with polyuria observed since birth. Laboratory tests showed persis-tent hypernatremia, elevated plasma and low urine osmolality. An attempt at oral administration of desmopressin had no effect, additionally copeptin level was in-creased. A genetic study (NGS of the AVP, AVPR2 and AQP2 genes) was taken and a new pathogenic variant in the AVPR2 gene (hemizygous c.157del) was detected. After the genetic test result was obtained, treatment with hydrochlorothiazide was started. The patient is now 3 months old, developing normally, weight and height are normal. Conclusions: A newborn with DI should be subjected to extensive multidisciplinary diagnostics including endocrine and renal causes. Copeptin evaluation and prompt genetic diagnosis allows for early diagnosis and implementation of appropriate treat-ment.