An Emerging Opportunistic Threat: A Rare Case of Mycobacterium Chimaera in a Non-surgical Patient With Both Fibrocavitary and Nodular Bronchiectatic Disease

Abstract Mycobacterium chimaera is a rare nontuberculous mycobacterium within the Mycobacterium avium complex responsible for indolent, yet life-threatening infection in immunocompromised patients and those with underlying lung disease. It gained global recognition due to its association with cardiothoracic surgery.1 We present an interesting case of Mycobacterium chimaera in a patient without history of cardiothoracic surgery or relevant risk factors, including underlying respiratory disease, with both fibrocavitary and nodular bronchiectatic features of disease. A 47-year-old male with a history of alcohol use disorder with recent relapse after being sober for eleven years presented after a fall. On presentation, he was afebrile with normal vitals and no leukocytosis. As a part of trauma workup, a CT chest was obtained, which revealed a right apical cavitary mass up to 8.6 cm with diffuse satellite nodules. He underwent bronchoscopy with endobronchial ultrasound for further evaluation. Blood/fungal/respiratory cultures, viral panel, HIV, and hepatitis panel were unrevealing. Cytology revealed no signs of malignancy. While awaiting AFB/mycobacterial cultures, given he was asymptomatic, he was discharged with infectious disease and pulmonary follow up. Subsequently, three mycobacterial cultures returned positive for Mycobacterium chimaera. He was noncompliant with follow up, but represented three months later with one month history of cough and back pain. He was afebrile with no leukocytosis and again had an unrevealing cardiopulmonary examination. CT chest revealed a cavity, now up to 9.0 cm, with increased wall thickness, increased reticulonodular infiltrates, and interspersed calcified granulomas (figure 1). He was started on a four-drug regimen with azithromycin, rifampin, and ethambutol for a minimum of one year and amikacin for up to twelve weeks. Mycobacterium chimaera is a rare nontuberculous mycobacterium associated with prolonged latency periods and nonspecific symptoms, making diagnosis challenging.1 Outcomes remain poor with reoccurrence rates up to 50% as well.2 This is despite aggressive and prolonged combination therapy, ideally with a macrolide, a rifamycin, ethambutol, and amikacin for greater than twelve months, if treatment is even tolerated.3M. chimaera has been associated with contaminated heater-cooler units in open-heart surgeries and cardiopulmonary bypass.3 Like other nontuberculous mycobacteria, it has fibrocavitary and nodular bronchiectatic phenotypes. Less commonly is there a combination of phenotypes as seen here, especially in the absence of risk factors.2 Given its rising incidence globally and occurrence in those without exposure history, as seen in this rare case, it is truly an emerging and fatal opportunistic threat. Resources: [1] doi:10.1016/j.jiac.2019.11.004 [2] doi:10.1183/13993003.02503-2016 [3] doi:10.1093/ofid/ofac287