Granulomatous Lung Inflammation of Unknown Causes Following COVID-19

Introduction Several studies have reported that COVID-19 increases the risk of autoimmune diseases, including sarcoidosis. Recently, we reported cases of pulmonary granulomatous inflammation distinct from sarcoidosis following COVID-19.Based on these observations, we hypothesize that COVID-19 may induce pulmonary granulomatous inflammation distinct from sarcoidosis. Methods We conducted a retrospective review of the medical records of adult patients (≥18 years) with pathologically confirmed noncaseating granulomas in the lung and/or thoracic lymph nodes (hilar or mediastinal) between January 2020 and August 2023. Results Fifty-four cases with pathologically confirmed noncaseating granulomas were identified. Specimens showing noncaseating granulomas were obtained by bronchoscopy in 36 cases (66.7%) and by surgery in 18 cases (33.3%). Three cases (5.6%) of noncaseating granulomas of unknown etiology were identified. Two of the three cases (3.7%) had a history of COVID-19 prior to the development of pulmonary granulomatous inflammation. Conclusion In the study, 5.6% of cases of noncaseating granulomatous inflammation in the lung and/or thoracic lymph nodes were of unknown etiology, and two of these cases (3.7%) had antecedent COVID-19. These findings suggest that COVID-19 may be associated with the development of pulmonary granulomatous inflammation distinct from sarcoidosis.