Ho Cheol Kim, et al : Mycobacterium Avium Complex Infection Presenting as an Endobronchial Mass in a Patient with Acquired Immune Deficiency Syndrome 217 Figure 4. Microscopic examination shows granulomatous inflammation with non-caseation necrosis (H&E, X200) (left). Acid-fast stain of the bronchial washing fluid demonstrates numerous mycobacterium within macrophages (Ziehl-Neelsen stain, X400) (right). Figure 5. After several months of treatment, the chest radiograph shows an improved left lung field (left), and the bronchoscopic examination shows mild fibrotic change without a mass lesion at the lingular division of the upper lobe bronchus (right). cultured from his expectorated sputum and bronchial washing fluid. The medication was then changed to rifabutin 150 mg/day, ethambutol 1,200 mg/day, and clarithromycin 1,000 mg/day. Two months after this change in treatment, the patient was asymptomatic and his chest radiograph was improved. Bronchoscopic examination showed mild fibrotic changes without the presence of a mass-like lesion at the lingular division of the left upper lobe (Figure 5). At this time, five months after the initiation of combination anti-retroviral therapy, his CD4 and CD8 cell counts were 227/mm3 and 828/mm3, respectively, and his CD4/CD8 ratio was 0.27. His viral load was less than 25 copies/mL. DISCUSSION This is the first report of an endobronchial mass caused by MAC infection in a patient with AIDS in the Republic of Korea. In a report on opportunistic infections of HIV/AIDS patients in the Republic of Korea, published in 2003, tuberculosis was the