A Fatal Case of Acute Respiratory Failure Caused by Mycobacterium massiliense
A 75-year-old man visited our hospital to treat pulmonary non-tuberculous mycobacterium (NTM) disease. He had complained productive cough for two months, and his diagnosis was confirmed by bacteriological analysis using sputum specimen. He was non-smoker and had no specific history of chronic diseases. His vital signs were normal. On physical examination, inspiratory crackles were heard on the right lower lung field. The results of blood test showed no definitive abnormality. A serologic test for human immunodeficiency virus was negative.\nChest X-ray revealed increased opacities in the right lower lobe (). Computed tomography scan of chest showed consolidation with air-bronchogram in the right lower lobe and focal centrilobular nodules on the right middle lobe (). On the bacteriological test, we verified the positive reactivity of acid fast staining in bronchial washing fluids. Moreover, we could find NTM DNA in the lung tissues obtained by percutaneous transthoracic needle biopsy using polymerase chain reaction. Finally, M. massiliense was identified from a sputum specimen and a bronchial washing sample, respectively, by a reverse blot hybridization assay. However, there was no evidence of growth for other bacteria, fungi, and virus in microbiological examination.\nAccording to the diagnositc criteria provided by the American Thoracic Society, he was diagnosed as M. massiliense pulmonary infection, and the treatment was started with clarithromycin, amikacin, imipenem, and doxycycline. But he rapidly developed a severe respiratory failure at 7 days after the initiation of medical treatment. Patient complained severe dyspnea with tachypnea, showing respiratory rate of 32 breaths per minute. Arterial blood gas analysis revealed that PO2, PCO2, pH, and PaO2/FiO2 ratio were 49.9 mm Hg, 25.4 mm Hg, 7.465, and 81 mm Hg, respectively. Chest X-ray showed diffuse bilateral infiltrates (). No improvement of gas exchange was obtained despite the support of mechanical ventilation, moreover, respiratory acidosis worsened to extreme levels. On the day 25 of diagnosis, the patient progressed to multi-organ failure resulting in his death.