A case of pulmonary Mycobacterium kansasii infection with pleural effusion, distinguished from pulmonary tuberculosis

A case of pulmonary Mycobacterium kansasii infection with pleural effusion is very rare. We report a case of pulmonary Mycobacterium kansasii infection with pleural effusion, distinguished from pulmonary tuberculosis. A 44-year-old man presented to a clinic with a productive cough, sputum, and loss of appetite for several months. Chest X-ray and chest computed tomography (CT) showed right pleural effusion, centrilobular nodules and infiltrative shadows with cavities in the bilateral lung fields. The direct smear examination showed positive acid-fast bacilli (Gaffky 5). He was referred to our hospital for suspected recurrent pulmonary tuberculosis. We started anti-tuberculosis drugs because pulmonary tuberculosis complicated with pleurisy was first suspected from the findings of high ADA level (78.6 IU/l) of the effusion and positive result of interferon-gamma release assay (QuantiFERON TB-2G). But Mycobacterium tuberculosis and M. avium complex was not identified by the polymerase chain reaction method and the culture of the sputum was negative. At a later date, Mycobacterium kansasii was detected by sputum culture. The patient was diagnosed as pulmonary Mycobacterium kansasii infection and treatment with anti-tuberculosis drugs including RFP resulted in a good clinical response. This case was a rare case of pulmonary Mycobacterium kansasii infection with pleural effusion, distinguished from pulmonary tuberculosis.