Study of histopathological and ultrastructural changes in the lungs of COVID-19 patients

Abstract

BackgroundCOVID 19 infection is a multi-systemic disease with the lungs bearing the maximum brunt. Very few autopsy studies have been done on the deceased patients. The present study aimed to study the clinical spectrum and lab parameters of COVID-19 patients along with the morphological spectrum of the lung changes in these patients by histology, Immunohistochemistry and Electron microscopy. We also compared the Clinical severity and Lab parameters with the histopathological phase of the lung involvement. MethodsWe conducted a cross sectional observational study between Jun 2021 to Dec 2022 where in needle necropsy of lung tissue of COVID 19 confirmed fatal cases were studied by histopathology, immunohistochemistry (using CD3, CD4, CD8, CD19, CD20, CD68 and Pan CK markers) and Electron microscopy. Various hematological, histopathological and ultrastructural parameters were studied. The results were analyzed using SPSS 25.0 software. ResultsA total of 24 cases were studied. The mean age was 65.9 yrs, male: female ratio was 2:1. Five had moderately severe COVID while 19 had severe COVID infection. Diffuse alveolar damage (DAD) was seen in 83% of all the cases. On the basis of clinical severity and histopathological staging, broadly two histopathological groups were made (Proliferative and Organizing). Difference between TLC, N/L ratio and L/Platelet ratio in two histopathological groups was assessed using unpaired t test, however no significant difference was noted. We did not find any correlation between clinical severity and histopathological groups though severe cases of COVID-19 were found to have a shorter time between admission to the hospital and death. All the biopsies were subjected to electron microscopy and in two of the cases we could demonstrate corona virus particles. ConclusionOur study has shown that severe cases of COVID 19 are associated with a shorter time between admission to hospital and death. While the histopathology of the lung showed diffuse alveolar damage as the most common finding; the Transmission Electron Microscopy (TEM) played an important role in characterizing the ultrastructure of these cells and demonstrating corona virus particles.