Pulmonary MAC infection in immunocompetent hosts generally manifests as cough, sputum production, weight loss, fever, lethargy, and night sweats. The onset of symptoms is insidious. Symptoms may be present for weeks to months. Many patients have only a chronic cough with purulent sputum production. Hemoptysis is rare in MAC infection. Less commonly, MAC has been associated with hot-tub lung, a type of hypersensitivity pneumonitis-like lung disease due to exposure to MAC in hot tubs.