Document Type

Conference Proceeding

Publication Date

5-1-2026

Abstract

Introduction/Objective Mycobacterium chimaera (M. chimaera), within the Mycobacterium Avium Complex (MAC), is a slow-growing nontuberculous mycobacterium (NTM) species that is most often characterized by nonspecific symptoms of night sweats, fever, and fatigue. Due to the nonspecific symptoms of M. chimaera and the rarity of this infection, delayed or misdiagnosis occurs in these patients. Risk factors of contaminated heater-cooler units used in cardiac surgery have been reported; however, cases without this exposure, such as this case, have been cited less commonly. This case of M. chimaera will present a young patient initially presenting with dyspnea who was found to have a hemorrhagic pleural effusion. Case Description A 39-year-old female with a medical history of horseshoe kidney, nephrolithiasis, and preeclampsia in her recent pregnancy presented to the emergency department with dyspnea and pleuritic, left-sided chest pain radiating to her back. The patient did not have leukocytosis on presentation, but did endorse several days of night sweats, fatigue, chills, and severe headache. Notably, the patient worked in a manufacturing plant that she described as having poor sanitary conditions. Initial chest x-ray and CT of the chest with contrast revealed a large left, slightly complex, pleural effusion. Ultrasound-guided diagnostic thoracentesis of the pleural effusion revealed hemorrhagic fluid with a lymphocytic predominance. Initial differential diagnoses were malignancy and infection. Additionally, a positive pregnancy test also made us consider ectopic pregnancy or gestational trophoblastic neoplasia. Later, a thoracotomy tube was placed in the left thoracic cavity. The patient was given tPA/dornase, and the chest tube output became milkier, which revealed pleural fluid with elevated triglycerides and cholesterol suggestive of chylothorax. The infectious workup was mostly unremarkable, except for two sputum cultures that grew M. chimaera. Specialty services, such as Obstetrics and Gynecology, Cardiothoracic Surgery, Interventional Radiology, Infectious Disease, and Pulmonology, contributed to diagnostic investigations and the management of this patient’s case. Discussion Diagnosis of M. chimaera can be difficult, especially given the nonspecific clinical presentation and lack of risk factors of cardiac surgery, as was seen in this case. The M. chimaera diagnosis was complicated by the pleural effusion that was changing in characterization and the positive pregnancy test that introduced other possible differentials. According to published articles, M. chimaera outbreaks have been reported from a contaminated heater-cooler unit manufacturer. These heater-cooler units are used for open-heart surgery, but this patient did not have a history of open-heart surgery. Initially, the differential was broad, including autoimmune, malignant, infectious, and gynecologic etiologies. However, the pleural fluid that reported a lymphocytic predominance and the sputum culture that grew M. chimaera helped to narrow the differential. Conclusion This case demonstrates the importance of having a broad differential for nonspecific presentations. These nonspecific presentations paired with a rare infection also require a high degree of suspicion in order to correctly make a diagnosis. It is essential to integrate clinical decision-making amongst the primary and consulting teams to identify rare infections. Hopefully, this case helps to make more providers aware of M. chimaera amongst patients without traditionally cited risk factors.

Comments

American College of Physicians Michigan Chapter and Society of Hospital Medicine Michigan Chapter 2026 Resident and Medical Student Day, May 1, 2026, Troy, MI

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