Histopathological features in fatal COVID-19 acute respiratory distress syndrome.

BACKGROUND: COVID-19 acute respiratory distress syndrome (ARDS) shares the common histological hallmarks with other forms of ARDS. However, the chronology of the histological lesions has not been well established. OBJECTIVE: To describe the chronological histopathological alterations in the lungs of patients with COVID-19 related ARDS. DESIGN: A prospective cohort study was carried out. SETTING: Intensive Care Unit of a tertiary hospital. PATIENTS: The first 22 consecutive COVID-19 deaths. MEASUREMENTS: Lung biopsies and histopathological analyses were performed in deceased patients with COVID-19 related ARDS. Clinical data and patient course were evaluated. RESULTS: The median patient age was 66 [63-74] years; 73% were males. The median duration of mechanical ventilation was 17 [8-24] days. COVID-19 induced pulmonary injury was characterized by an exudative phase in the first week of the disease, followed by a proliferative/organizing phase in the second and third weeks, and finally an end-stage fibrosis phase after the third week. Viral RNA and proteins were detected in pneumocytes and macrophages in a very early stage of the disease, and were no longer detected after the second week. LIMITATION: Limited sample size. CONCLUSIONS: The chronological evolution of COVID-19 lung histopathological lesions seems to be similar to that seen in other forms of ARDS. In particular, lung lesions consistent with potentially corticosteroid-sensitive lesions are seen.