<s>[INST] context: This chest x-ray shows hyperlucent lung fields with flattened diaphragm. Areas of vascular attenuation are noted especially in the upper zones, consistent with central lobar emphysema. A 3.5 x 3-cm circular cavitary shadow is seen in the right upper zone with elevation of the horizontal fissure and the right hilum. An upper lobe cavitary lesion in a patient with underlying COPD suggests TB or NTM (MOTT). AFB-positive smears may culture out Mycobacterium kansasii or M. avium-intracellulare complex (MAC). Another possibility is nocardia infection. Actinomyces can present as upper lobe cavitary disease but is not acid-fast-positive on smear and is commonly seen with skin infection and fistula formation. The diagnosis of M. avium disease (MAC) is established by fulfilling clinical radiographic and culture criteria. The diagnosis should be suspected with symptoms of cough, fever, and weight loss with progressive infiltrates, cavitation, and multiple nodules. Patients without underlying lung disease who have chronic pulmonary infections are predominantly women and nonsmokers. High-resolution CT scan typically shows multiple small nodules with bronchiectasis. The diagnosis must be established bacteriologically since some nontuberculous mycobacteria are commonly found in nature and contamination of specimen can occur. Therefore, the diagnosis of MOTT pulmonary disease requires the following: three positive cultures with negative AFP smears; two positive cultures and one positive smear; a single bronchial specimen with a positive culture of 2 to 4+ growth; a positive AFB smear and a positive culture of any biopsy specimen; granuloma by biopsy with one positive culture from any respiratory specimen; or a growth of MAC from any usually sterile extrapulmonary site. Although transient infection with spontaneous resolution occurs, significant growth on culture means disease is present. Mycobacterial disease due to nontuberculous mycobacteria is now more common than tuberculosis in the United States. It is generally prevalent in specific areas such as the Southeast and the Gulf Coast region. According to the CDC, one-third to onefouh of all isolates of mycobacteria are due to nontuberculous mycobacteria. Natural waters appear to be the likely environmental source of these organisms, which can be isolated from tap water or even hospital water. Person-to-person transmission is thought to be unlikely. Clinical syndromes of MAI disease in nonimmune non-HIV individuals occur in older patients, paicularly smokers and alcoholics with COPD. These syndromes may present as upper lobe infiltrates or cavitary or solitary nodules.Patients can develop chronic bronchiectasis or cystic fibrosis. In nonsmoking women older than 50, multiple small and medium-sized nodules may be seen. Upper lobe or lingular infiltrates have been described. Coughing and purulent sputum for an average of 6 mo may be present. [/INST] question: A 60-year-old man with a history of COPD and old TB is seen with mild hemoptysis and chronic cough. He is HIV negative and has been ill for about 2 wk. Vital signs: pulse 110 bpm; temperature 101degF; respirations 24/min; blood pressure 108/70 mm Hg. No skin lesions are noted. Laboratory data: Hb 14 g/dL; HCA 42%; WBCs 8.7/uL; BUN 24 mg/dL; creatinine 0.8 mg/dL; sodium 131 mEq/L; potassium 4.3 mEq/L. ABGs on RA: pH 7.37; PCO2 43 mm Hg; PO2 87 mm Hg. Sputum tests reveal numerous AFBpositive organisms on smear. Spirometry shows an obstructive ventilatory impairment with marginal reversibility. CXR is shown . Among the choices listed, the most likely diagnosis is | options: A: Lung abscess B: Non-TB mycobacteria C: Actinomycosis D: Aspiration pneumonia | answer: B </s>