[Inappropriate antidiuretic hormone secretion in pulmonary nocardiosis].

An 81-year-old woman with a medical history of hypertension, hypercholesterolemia, childhood pulmonary tuberculosis, bronchiectasis, and depression presented at our hospital reporting dyspnea on slight exertion, cough, and yellowish expectoration of 4 days’ duration. On physical examination, the patient was alert, oriented, afebrile, and normotensive. Bilateral wheezing was noted on auscultation. No edema was observed and findings from abdominal and neurological examinations were normal. Arterial blood gas analysis showed a pH of 7.37, PaO2 of 55 mm Hg, PaCO2 of 45 mm Hg, and an oxygen saturation of 88%. Blood tests revealed an elevated white blood cell count (29 800 cells/μL) with a normal differential profile and a sodium concentration of 128 mEq/L; the other values analyzed were normal. A chest radiograph revealed residual lesions from healed tuberculosis in the right upper lobe and a new pulmonary infiltrate in the left lower lobe (Figure). N asteroides sensitive to the antibiotics tested was isolated from sputum. The other microbiological tests were negative. Antibiotics (co-trimoxazole, imipenem, meropenem, and aminoglycosides) were administered as part of the treatment regimen. The patient initially showed improvement, but her condition deteriorated over the following days as she developed severe hyponatremia (sodium concentration, 116 mEq/L) due to SIADH (plasma osmolality, 246 mOsm/kg; urine osmolality, 421 mOsm/kg; urinary sodium, 169 mEq/L). A computed tomography (CT) scan of the head revealed no abnormal findings. Sodium plasma levels improved after fluid intake was restricted and perfusion with 3% hypertonic saline solution was performed; nevertheless, after 27 inpatient bed-days, the patient suffered cardiorespiratory arrest and failed to respond to cardiopulmonary resuscitation.