Pleural mycobacterium avium complex infection in an immunocompetent female with no risk factors

Mycobacterium avium complex (MAC) infections rarely affect the pleura, accounting for 5-15% of pulmonary MAC. We report a case of MAC pleural effusion in an otherwise immunocompetent young patient. A 37-year-old healthy female with no past medical history was admitted to the hospital with two weeks of right sided pleuritic chest pain, productive cough, and fever. She was febrile, tachycardic, and tachypneic with signs of right sided pleural effusion which were confirmed by chest X-ray and chest CT. Thoracentesis revealed lymphocytic predominant exudative fluid. The patient underwent pleural biopsy, bronchoscopy with bronchoalveolar lavage, and video assisted thoracoscopic surgery (VATS), all of which failed to identify the causative organism. Six weeks later, MAC was identified in the pleural fluid and pleural biopsy by DNA hybridization and culture. The patient was started on clarithromycin, ethambutol, and rifampin. After six months of treatment, she was asymptomatic with complete radiological resolution of the effusion. The presence of lymphocytic effusion should raise the suspicion for both tuberculous and nontuberculous mycobacterial disease. Pleural biopsy must be considered to make the diagnosis. Clinicians must maintain a high index of suspicion of MAC infection in an otherwise immunocompetent patient presenting with a unilateral lymphocytic exudative effusion.