Long COVID in Immunocompromised and Immunocompetent Patients: A Clinical, Morphologic, and Virologic Portrait

Coronavirus disease 2019 (COVID) primarily affects the lung and can lead to chronic/post-COVID syndrome. Some insights about late pulmonary changes occurring in patients recovering from COVID have been published, but the evidence of detailed pathologic changes coming from follow-up care patients with long COVID is limited.

To evaluate tissue morphologic and viral features in transbronchial biopsies of long COVID patients (immunocompetent and immunocompromised).

This retrospective observational study included 18 patients (9 immunocompetent and 9 immunocompromised) who were consecutively referred to our outpatient clinic for post-COVID pneumonia, undergoing transbronchial biopsy. Several histologic changes were analyzed by computer-assisted morphometric analysis. As organizing pneumonia (OP) was consistently detected, fibrosis and inflammation were also evaluated in transbronchial biopsies from 28 control patients with histologic confirmation of OP. Tissue SARS-CoV-2 and the subgenomic transcripts were investigated. Morphologic findings were correlated with clinical and radiologic data.

Long COVID patients showed lower inflammation than controls (P < .001) despite a similar fibrotic extension. When considering separately the 2 long COVID groups, the same inflammatory infiltrate extension was found, whereas a higher fibrotic remodeling characterized the immunocompetent subgroup (P = .05). Molecular investigation showed that SARS-CoV-2 was present in tissue samples obtained from 3 long COVID patients.

Long COVID patients showed a peculiar OP pattern, with more vascular and fibrotic changes. SARS-CoV-2 RNA, even in replicative status, can be detected in lung biopsies of both immunocompetent and immunocompromised patients. This pilot study is a forerunner of more in-depth lung tissue investigations to gain a better understanding of long COVID pathobiology.