CENTRAL DIABETES-INSIPIDUS ASSOCIATED WITH A MISSENSE MUTATION IN THEARGININE-VASOPRESSIN GENE THAT REPLACES ALA AT THE CARBOXYTERMINUS OFTHE SIGNAL PEPTIDE WITH THR

We report an 18-year-old male with a history of polyuria, polydipsia, and thirst since childhood. In a hypertonic saline infusion test, the patient's plasma vasopressin rose only to 0.28 pg/ml, In a water depri vation test, his urinary osmolality rose only to 189 mosmol/kg and the n rose to 538 mosmol/kg by vasopressin administration. A T1-weighted m agnetic resonance imaging (MRI) scan revealed a loss of the posterior pituitary bright spot. Sequencing of the vasopressin gene showed a het erozygous point mutation that replaced Ala at the carboxyterminus of t he signal peptide with Thr, His father also had similar history, and w e therefore diagnosed his illness as familial central diabetes insipid us.