Diagnosis of arginine vasopressin deficiency in a patient with 10 years of polyuria and polydipsia following an Epstein-Barr virus infection.

Polyuria-polydipsia syndrome is composed of arginine vasopressin deficiency, arginine vasopressin resistance and primary polydipsia and are characterised by severe polyuria with hypotonic urine. The water deprivation test is commonly used to indirectly assess the vasopressin response to water deprivation. We report a woman in her 20s who demonstrated severe polyuria (11-12 L/day) on submitting a 24-hour urine sample for analysis. She subsequently mentioned having had polyuria and polydipsia for 10 years after an Epstein-Barr virus infection. A water deprivation test with copeptin measurement confirmed arginine vasopressin deficiency. Treatment with desmopressin transformed her life. Further investigation revealed possible concurrent subclinical mixed connective tissue disease. We suspect Epstein-Barr virus infection to be the cause of the arginine vasopressin deficiency and possibly the trigger for the subclinical mixed connective tissue disease. This case also highlights the utility of copeptin measurements in differentiating the various polyuria-polydipsia syndromes.