218 The Korean Journal of Internal Medicine : Vol. 22, No. 3, September 2007 third most common opportunistic infection, and was the most common initial infection identified when patients first presented with AIDS12). Atypical mycobacterial infection accounted for only six cases (4%) in 150 AIDS patients, and the specific type of atypical mycobacterium was not described12). There has been one case report of Mycobacterium avium complex-intracellular (MAI) meningoencephalitis in a patient with AIDS and preexisting disseminated MAC infection from the Republic of Korea13). There was a recently published report of endobronchial lesions caused by Mycobacterium avium Infection in an immunocompetent 21-year-old patient with no preexisting lung disease14). Although isolated pulmonary involvement with MAC is relatively common in immunocompetent hosts, it is uncommon in patients with AIDS11). Because isolated pulmonary involvement with MAC is rare, and given the high frequency of colonization in bronchial trees, histological confirmation is required to support positive cultures from respiratory specimens15). For the patient reported here, several sputum cultures and the bronchial washing fluid culture showed mycobacterium, specifically MAC, and the histological examination showed granulomatous inflammation with epitheloid cells in the bronchoscope biopsy specimen. Because the histological examination usually does not distinguish M. tuberculosis from MAC, culture for mycobacterium is required to confirm MAC infection15). At first, a malignant tumor was suspected because the lung and bronchoscopic findings showed a polypoid mass that completely occluded the lingular division of the left upper lobe of the lung. However, the diagnosis of pulmonary infection with MAC was confirmed by repeated sputum culture, bronchial washing fluid culture, and histological examination. It has been suggested that endobronchial disease with MAC results from the restoration of the immune response during anti-retroviral therapy (immune reconstitution syndrome)8, 16, 17). It has been hypothesized that patients may experience a subclinical infection that becomes clinically manifest as host cellular immunity recovers after the initiation of anti-retroviral therapy. This suggests that the host immune response is a cofactor in causing disease. When MAC infection is due to the immune reconstitution syndrome, the symptoms are expected to appear within two to four weeks after the initiation of anti- retroviral therapy. The patient reported here was diagnosed with P. carinii pneumonia and CMV pneumonia prior to the diagnosis of MAC infection. Following diagnosis, the patient was started on anti-retroviral therapy. After several months of anti-retroviral therapy, isolated pulmonary infection with MAC developed. In this case, the development of MAC infection, after the initiation of anti-retroviral therapy, occurred over a longer interval than that reported previously16, 17). The clinical features of isolated pulmonary MAC infection in patients with HIV include: fever, cough, and night sweats, and are often accompanied by dyspnea, hemoptysis, and/or weight loss. Radiographic patterns have included mediastinal adeno- pathy, patchy bilateral alveolar infiltrates, nodular infiltrates, and normal findings on chest roentgenograms. Blood cultures are normally negative for MAC18). Treatment of isolated pulmonary MAC infection is usually successful, with favorable outcomes described in 21 of 21 reported cases11, 19). In conclusion, patients with HIV/AIDS who present with respiratory symptoms and a chest radiograph with lung infiltrates and adenopathy during anti-retroviral therapy should be evaluated for potentially isolated pulmonary MAC infection. REFERENCES 1) Benator DA, Gordin FM. 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