Endobronchial Mycobacterium avium Infection in an Immunocompetent Patient
A 59-year-old woman was referred to the pulmonary department for evaluation of an abnormal finding detected on chest radiography and chest computed tomography (CT) during routine long-term follow-up for cancer. The patient had been diagnosed with cervical cancer and received surgery and adjuvant chemotherapy 10 years earlier. She had also undergone endoscopic mucosal resection for early stage rectal cancer two years ago. Since then, she has shown no evidence of recurrence of these cancers. Initially, during the routine follow-up, the patient displayed no abnormalities either in subjective symptoms or on physical examination. However, chest radiography and chest CT revealed multiple pulmonary infiltrates in the left lingular division and left lower lobe (). The complete blood cell count (CBC) and blood chemistry revealed the following: white blood cell (WBC) count of 4.87 × 103/mm3, with 69.8% neutrophils and 17.9% lymphocytes; platelet count of 283 × 103/mm3; hemoglobin level of 10.9 g/dL; aspartate transaminase level of 25 U/L; alanine transaminase level of 16 U/L; and total bilirubin level of 0.6 mg/dL. Anti-HIV antibody was negative. The patient was treated with empirically with antibiotics (amoxicillin/clavulanate), but did not show any interval changes on chest radiography. We recommended regular check-ups to monitor for any changes in the pulmonary lesions or other symptoms. Six months later, we performed follow-up chest radiography and chest CT. Although the patient still had no respiratory symptoms, chest images showed that the multiple pulmonary infiltrates had worsened (). We performed a bronchoscopic evaluation to obtain a differential diagnosis. Bronchoscopic examination revealed a white- and yellow-colored irregular mucosal lesion in the bronchus of the left lingular division (). Bronchoscopic biopsy of the endobronchial lesion showed chronic granulomatous inflammation with caseous necrosis, a typical and consistent feature of mycobacterial histopathology (). Acid-fast bacilli (AFB) staining was positive in bronchial washing fluid. However, the result of a real-time polymerase chain reaction (PCR) assay to detect M. tuberculosis was negative despite the use of a specimen that stained positive for AFB. Cytology for bronchial washing fluid was normal. Considering the slowly progressing nature of NTM pulmonary disease, we decided to postpone treatment, pending the results of AFB cultures. After two months, cultures of sputum and bronchial washing fluid grew NTM, and M. avium was identified in both of the specimens. In the meantime, the patient developed respiratory symptoms, including cough, sputum, and slight hemoptysis. Thus, antimycobacterial therapy was initiated with 500 mg of clarithromycin, 450 mg of rifampicin, and 800 mg of ethambutol daily. After two months of treatment, the patient no longer had respiratory symptoms and the infiltration of the left lower lobe on chest radiography had decreased. At time of this study, the patient was continuing to receive antimycobacterial therapy, without significant adverse reactions.