Case of severe motor and intellectual disabilities presenting with partial central diabetes insipidus triggered by infection

: We report a 42-year-old woman with severe motor and intellectual disabilities (SMID) who showed partial central diabetes insipidus during severe pneumonia. Serum sodium levels were previously within the upper normal range from 140 to 147 mEq/L. During pneumonia, however, serum sodium rose rapidly to reach 185 mEq/L. The daily urinary volume exceeded the daily intake of water. Nasal administration of 1-desamino-8-D-arginine vasopressin (DDAVP) reduced the daily urinary volume and the serum sodium level to normal ranges. Consequently, we diagnosed her as having central diabetes insipidus (DI). She required a smaller dose of DDAVP (2.5 microg/day) than usual DI (5-15 microg/day) to maintain normal urinary volume and the serum sodium level for seven months. After the nasal administration of DDAVP was discontinued, the serum sodium levels again returned to within the upper normal range. A water deprivation study demonstrated poor elevation of both plasma antidiuretic hormone (ADH) level (range, 0.5-2.0 pg/ml) and urine osmolarity (peak level, 552 mOsm/kgH2O) despite the elevation of plasma osomolarity, suggesting latent partial central DI. Water balance and serum electrolyte levels should be closely monitored in cases of SMID.