To the Editor.
—We recently had the opportunity to examine a patient previously described in the Archives.1 The patient, a 38-year-old man, developed polyuria and hypodipsia four days after the onset of an upper respiratory tract infection in 1974. Water deprivation test results following the protocol of Miller et al2 were compatible with the diagnosis of partial central diabetes insipidus (DI). Skull roentgenograms, electroencephalogram, and lumbar puncture were normal. The patient's polyuria and hypodipsia resolved without treatment, but his serum osmolarity remained elevated at 304 mOSM/kg for an additional year. To our knowledge, this was the first reported case of transient DI with prolonged serum osmolarity elevation caused by an acute, febrile illness. The mechanism responsible for this phenomenon was not elicited.In the past ten years, the patient has remained asymptomatic. Physical examination findings have been normal. Routine laboratory study results have also been normal, including recent