B73-08 A Rare Case of Actinomyces-Associated Fibrosing Mediastinitis: A Review of Classic Imaging Findings and Treatment

Abstract Introduction Fibrosing mediastinitis is an uncommon condition of progressive proliferation of fibrous tissue within the mediastinum that is often benign but can cause significant issues with the pulmonary architecture. It is commonly associated with prior tuberculosis and histoplasmosis infections, autoimmune syndromes, prior radiation, or drug exposures (1). Classic radiographic features of fibrosing mediastinitis include bronchial airway narrowing, pulmonary artery stenosis, and esophageal narrowing (2). In severe cases, patients can develop pulmonary hypertension due to the structural pulmonary vessel compression that occurs with mediastinal remodeling (3). Case A seventy-year-old male with a past medical history of congestive heart disease, chronic obstructive pulmonary disease (COPD), and prior tuberculosis infection status post treatment presented to the hospital in acute hypoxic respiratory failure complicated by a recurrent large, right pleural effusion. He had undergone multiple drainages and trials of diuresis without improvement in his symptoms. Fluid studies on multiple drainages demonstrated a pseudo exudative effusion with positive Light’s criteria by elevated protein in the setting of diuresis. Cytology was negative. His case was complicated by trapped lung physiology after repeated thoracentesis and required chest tube placement. Computed Tomography (CT) imaging (See Figure 1) showed bronchial narrowing, esophageal narrowing, and pulmonary artery stenosis. Differential diagnosis at the time included decompensated heart failure, malignancy, and possibly infection given his abnormal mediastinal architecture despite his unrevealing fluid studies. He ultimately underwent a Video-Assisted Thoracoscopic Surgery (VATS) washout with pleural biopsy and culture, which was positive for Actinomycosis. He had poor dentition, and it was thought that this could have been the initial nidus of infection. He was initiated on intravenous Penicillin G for six weeks and was transitioned to Augmentin oral therapy for one year. He had serial CT imaging that documented improvement while taking his prescribed antibiotic treatment (See Figure 1). He continues to follow with Pulmonology and Infectious Disease for serial imaging and antibiotic management. The patient has since developed significant right-sided heart dysfunction with concern for pulmonary hypertension, which can be due to his underlying heart disease or can be a further complication of fibrosing mediastinitis. Discussion The present case serves as a unique example of classic fibrosing mediastinitis related to severe actinomyces infection, which is an extremely rare cause of fibrosing mediastinitis. Case reports do exist but suggest the incidence of this kind of infection leading to fibrosing mediastinitis is in the single digits (4). This abstract is funded by: None