Pleural Mycobacterium Avium Complex (MAC) Empyema: A Rare Presentation of Disseminated Mac Infection in a Patient With Systemic Lupus Erythematosus/Dermatomyositis Overlap

Abstract Background: Mycobacterium avium complex (MAC) infection is an uncommon cause of empyema. This case highlights a 26-year-old male with SLE and dermatomyositis overlap syndrome who presented with pleural effusions, illustrating the diagnostic challenges and management complexities associated with MAC. Presentation: A 26-year-old male with a history of Systemic Lupus Erythematosus (SLE) and dermatomyositis was referred to the emergency department for workup of bilateral pleural effusion seen on computed tomography (CT) chest imaging. A prior CT for lung nodule screening had shown moderate to large partially loculated effusions, left-sided pleural thickening, and compressive atelectasis. On current presentation, he was afebrile and denied additional symptoms. Left diagnostic thoracentesis yielded a turbid pleural fluid. Pleural fluid analysis indicated a white blood count (WBC) of >80,000 (neutrophilic predominance), elevated lactate dehydrogenase (LDH) (2826 IU/L), and low glucose (<2 mg/dL). Acid-fast bacilli (AFB) staining was positive, leading to initial tuberculosis treatment. A left sided chest tube was placed and removed after four days. Further review of chest imaging showed that the right sided pleural effusion has a more acute development and was thus managed via therapeutic thoracentesis along with antibiotic coverage for tuberculosis. The patient was discharged on RIPE (rifampin, isoniazid, pyrazinamide, and ethambutol) therapy. However, four weeks later, pleural cultures confirmed MAC. Treatment was adjusted to clarithromycin, ethambutol, and rifabutin. Despite this, he returned to the ED 3 months later with recurrent loculated pleural effusions bilaterally. A right sided thoracentesis yielded a purulent aspirate that showed a WBC count of 61,250, LDH of 2094 IU/L, RBC 233,000, total protein 4.3, low glucose, triglycerides 127, pleural deaminase of 392, and a positive AFB stain. The patient underwent a right sided pleuroscopy showing extensive fibropurulent exudates. Bilateral thoracostomy was performed with resolution to left pleural effusion only. Due to rapid fluid accumulation, surgical intervention via video-assisted thoracic surgery (VATS), which revealed a severely thickened pleural rind, with subsequent placement of three chest tubes was performed and removed 17 days later. He is currently treated with rifabutin, ethambutol, azithromycin, and amikacin with close monitoring via pulmonology, rheumatology, and infectious disease. Conclusion: This case illustrates an atypical presentation of an uncommon infection, specifically the complexities of managing MAC empyema in immunocompromised patients with autoimmune disorders. While MAC infections are rare, their prevalence in immunocompromised patients is increasing, warranting high index of suspicious and aggressive treatment. Importantly, further research into optimal management is needed.