[Inappropriate secretion of antidiuretic hormone disclosing acute intermittent porphyria]

The authors report a case of acute intermittent porphyria in a 31-year old woman, revealed by inappropriate secretion of the antidiuretic hormone, a diagnosis confirmed by radioimmunoassay. Measurements of red cell urosynthetase made the diagnosis of porphyria certain and showed that the disease was familial, although clinically asymptomatic. Antidiuresis is not the only cause of hyponatraemia in acute intermittent porphyria. Similarly, psychic disorders are frequent in SIADH, but they are not necessarily due to acute intermittent porphyria.