Does COVID-19 pneumonia signify secondary organizing pneumonia?: A narrative review comparing the similarities between these two distinct entities

Abstract

Multiple observational studies have described the similarities between COVID-19 pneumonia and organizing pneumonia (OP). These two entities clinically manifest with mild and subacute respiratory symptoms, often with a delayed diagnosis due to the atypical ARDS and silent hypoxemia presentation. Radiological features are often indistinguishable between the two. With the increase in antemortem lung biopsies and autopsies being performed, more histopathological findings of OP and its variant, acute fibrinous and organizing pneumonia (AFOP), are being diagnosed. These entities are known complications of viral infections as a delayed immunological process, explaining the favorable response to corticosteroids. Clinicians should be vigilant to diagnose this under-recognized entity of secondary OP in people with COVID-19 when clinical deterioration occurs, especially with compatible radiologic findings and recent cessation of corticosteroids. Despite the proven benefits of corticosteroids in treating COVID-19, treatment approaches can be more effective as OP often requires higher doses and a more prolonged therapy duration for remission and preventing relapses. The purpose of our narrative review is to compare the similarities between COVID-19 pneumonia and OP, emphasizing the clinical, radiological, and histopathological features based on the evidence available in the literature.

Keywords: COVID-19; Coronavirus disease 2019; Organizing pneumonia; SARS-CoV-2; Secondary organizing pneumonia; Severe acute respiratory syndrome coronavirus 2.

Fig. 1

Multiple intra-alveolar buds of granulation tissue, termed Masson Bodies (black arrow), containing fibroblasts and myofibroblasts mixed with a loose connective matrix extending into the lumen of distal bronchioles consistent with organizing pneumonia.

Fig. 2

Overview of the possible silent hypoxemia (happy hypoxemia) mechanism in COVID-19 and organizing pneumonia patients. This figure was created using Servier Medical Art templates, which are licensed under a Creative Commons Attribution 3.0 Unported License; https://smart.servier.com.

Fig. 3

Similarities between the radiological features of organizing pneumonia and COVID-19 pneumonia. (A) Chest radiograph showing bilateral opacities predominantly in the lung peripheries. (B) Chest CT demonstrating bilateral lower lobes consolidation in the subpleural regions. (C) Chest CT revealing bilateral, peripheral, ill-defined patchy GGOs and consolidations in a perilobular pattern. Reverse-halo signs (black arrow) are seen peripherally.