[A case of mild pulmonary tuberculosis complicated with the syndrome of inappropriate antidiuretic hormone secretion which caused impaired consciousness].

An 81-year-old woman was admitted to our hospital for hyponatremia and impaired consciousness after unsuccessful antibiotic treatment for pneumonia-like symptoms by a previous doctor. A chest X-ray film revealed unilateral infiltration. Mycobacterium tuberculosis was detected on a sputum smear and pulmonary tuberculosis was diagnosed. Based on the diagnostic criteria, we believed that her hyponatremia a consequence of syndrome of inappropriate antidiuretic hormone secretion (SIADH) as a complication of pulmonary tuberculosis. Sodium loading and water restriction quickly improved her serum sodium level and impaired consciousness. Anti-tuberculosis therapy reduced the abnormal shadows noted on chest X-ray films, and the sputum smear became negative for Mycobacterium tuberculosis. Her serum sodium level remained normal after the discontinuation of sodium loading. Previous reports have associated SIADH with severe types of tuberculosis such as miliary tuberculosis, tuberculosis meningitis, and pulmonary tuberculosis with massive bacterial excretion. However, this complication can also occur in mild tuberculosis, as in this case, thus SIADH should also be considered in mild cases of tuberculosis.