D107-22 A Secondary Igg4-sclerosing Inflammatory Pseudotumor of the Lung

Abstract IgG4-related disease is a fibroinflammatory condition characterized by tumor-like lesions throughout the body. Lesions are comprised of IgG4-positive plasma cell infiltration and fibrosis,with commonly elevated serum IgG4 concentrations. Multiple, distinct immune mechanisms underlie it pathophysiology including reports of molecular mimicry to bacterial pathogens. We discuss a case of an undertreated bacterial empyema evolving into a secondary IgG4-sclerosing pseudotumor of the lung.A 50-year-old female without significant past medical history presented to an outside hospital with two weeks of fever, cough, shortness of breath and fatigue. She was diagnosed with community acquired pneumonia complicated by a left-sided parapneumonic effusion and was discharged home with a 10-day course of oral antibiotics. She presented to her primary care physician 2 months later with continued symptoms, underwent chest radiography, which was notable for a persistent left-sided pleural effusion, and was, again, treated with a 10-daycourse of oral antibiotics. She presented to our general pulmonary clinic approximately 6months following her initial presentation, having undergone an MRI of the chest ordered by her primary care physician for continued cough and dyspnea. Figure 1. She underwent thoracentesis notable for thick, purulent fluid which grew gram positive cocci. She was admitted to the hospital, a chest tube was placed, and she was initiated on IV antibiotics and intrapleuralTPA/DNase. Due to poor drainage and continued sepsis, she underwent an open thoracotomy with washout and decortication. A 6-7 cm thick pleural rind with a gelatinous interior was found to be encasing much of the left lung, disrupted by pockets of tenacious fluid housing gram-positive cocci. Pathologic examination revealed dense fibrosis, granulation tissue, and acute/chronic inflammation with 40% IgG4-positive plasma cells. Her disease process was favored to represent an under-treated empyema that evolved into a secondary IgG4-sclerosinginflammatory pseudotumor. She underwent PET/CT approximately 2 months after surgery which confirmed no focal metabolic activity and a well inflated left lung with only patchy areas of atelectasis. A secondary rheumatologic work was not obtained due to loss in follow up.This case demonstrates a rare complication of misdiagnosis or under-treated infections within the lung and pleural space. It highlights multiple imaging modalities of potential use for characterization of abnormal findings in the pleural space as well as the importance of histopathology for the appropriate diagnosis. This abstract is funded by: None