Adipsic Hypernatremia Syndrome in Infancy

We report on an infant with chronic hypernatremia due to a congenital defect in osmo-regulation of thirst and the secretion of arginine vasopressin (AVP). A 12 month-old female infant who presented with irritability and signs of dehydration was found to have hypertonic dehydration; plasma osmolality was 430 mOsm/kg B.W. Despite rehydration she remained hypernatremic (serum Na+ 152-158 mEq/l). Lack of signs of thirst led us to the diagnosis of chronic hypernatremia due to adipsia. Laboratory investigation showed: 1. plasma AVP levels were low for plasma osmolality; 2. urine osmolality was normal for plasma AVP, and 3, there was a significant correlation of plasma to urine osmolality (r = 0.72, p < 0.02); however, the slope was markedly reduced indicating partial destruction of the AVP osmoreceptors.