[Case of SIADH caused by ethionamide in a patient with pulmonary tuberculosis]

Cases of syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with tuberculosis have been reported, however, in most of these cases, tuberculosis disease is miliary or severe. Here we report the first case of SIADH induced by ethionamide (TH). The case is a 76 year-old woman. She noticed cough in April 2004 and chest X-ray showed infiltrative shadows on the right upper lung field. Sputum examination revealed positive for TB-PCR, and she was referred to our hospital. Treatment was started with the combination of isoniazid (INH), rifampicin and ethambutol, however susceptibility test showed the bacilli were resistant to INH, then INH was replaced by TH on day 59. Loss of appetite developed 4 days later, the level of consciousness dropped to Japan Coma Scale II-20, and the Na concentration decreased to 113 mEq/l 6 days later. We made the diagnosis of SIADH based on the diagnostic criteria. She recovered from SIADH by the replacement of TH with SM, the restriction of water intake, and the loading of Na. Judging from the coincidence of the administration of TH and the onset of SIADH, no recurrence of SIADH after the cessation of TH, the mildness of tuberculosis, and the onset of SIADH in an already recovered case, we thought that SIADH in this case was causedly TH. Not only adrenal insufficiency but also SIADH should be considered when patients with tuberculosis show hyponatremia, and drugs on use should be reviewed as the possible cause of SIADH.