[Clinical, radiological, and histopathological features of pulmonary post-COVID syndrome : A form of autoimmune-mediated interstitial lung disease?]

BACKGROUND About 10% of patients develop persistent symptoms after mild/moderate COVID-19. We have previously reported detection of antinuclear autoantibodies/extractable nuclear antigens (ANA/ENA) in patients with severe COVID-19. OBJECTIVES The aim of this small pilot study was to characterize long-/post-COVID and to evaluate possible similarities between lung involvement in long-/post-COVID and connective tissue disease (CTD). METHODS We prospectively enrolled 33 previously healthy patients with persistent pulmonal symptoms after mild/moderate COVID-19 without hospitalization (median age, 39 years). We performed clinical evaluation including pulmonary function tests, computed tomography (CT), and serology for ANA/ENA. In 29 of 33 patients, transbronchial biopsies (TBBs) were taken for histopathological assessment. RESULTS Most patients presented with disturbed oxygen pulse in spiroergometry and slight lymphocytosis in bronchoalveolar lavage (BAL) fluid. The CT pattern showed bronchial wall thickening and increased low-attenuation volume. Autoantibodies were detected in 13 of 33 patients (39.4%). Histopathological assessment showed interstitial lymphocytosis with alveolar fibrin and organizing pneumonia. Ultrastructural analyses revealed interstitial collagen deposition. CONCLUSION While histopathology of pulmonary long-/post-COVID alone is unspecific, the combination with clinical and radiological features together with detection of autoantibodies would allow for a diagnosis of interstitial pneumonia with autoimmune features (IPAF). Since we observe interstitial collagen deposition and since IPAF/CTD-ILD might progress to fibrosis, the persistence of autoantibodies and possible fibrotic change should be closely monitored in autoantibody-positive long-/post-COVID patients.