Thoughts on mastocytosis in COVID-19: an author's response

Boaz Lopuhaa*, Jan H. von der Thüsen

*Corresponding author for this work

Research output: Contribution to journalComment/Letter to the editorAcademicpeer-review

Abstract

We thank the author for taking the time to review our work. While we did not establish a causal relationship between the increase in mast cells and thrombosis and pulmonary fibrosis, we think the significant difference in mast cells could play a role in both. We acknowledge that it could be a minor role, as a variety of different factors could contribute to the high occurrence of thrombosis and fibrosis, as pointed out by the author. Recent studies suggested that mast cells contribute to pulmonary fibrosis and thrombosis. However, we take into account that this association could also represent a postinflammatory non-canonical process; a high number of mast cells in SARS-CoV-2-infected lung tissue may be secondary to immune activation, and not necessarily to immune dysregulation. Further studies—perhaps with gene knockout experiments—should investigate to what degree an increase in mast cells is part of a normal physiological feedback in response to viral infection in the lung.
Regarding the influence of obesity in tryptase levels, we think that the relatively high amount of obese patients in COVID-19 may have had an influence on results. Unfortunately, we had limited influenza control samples to compensate. Although Goldstein et al. describe an increase of tryptase in serum, we have found a significant increase of tryptase and chymase-positive cells in lung tissue, which we believe to be intrapulmonary mast cells instead of tryptase (and chymase) from extrapulmonary mast cells. In similar fashion, Giannetti et al. based their findings on serum tryptase, and not directly at intrapulmonary abnormalities. Although its impact on the pathophysiology of COVID-19 remains uncertain, we regard the increase of intrapulmonary mast cells as a potential factor contributing to COVID-19 pathophysiology.
Original languageEnglish
Pages (from-to)479-480
Number of pages2
JournalHistopathology
Volume86
Issue number3
DOIs
Publication statusPublished - Feb 2025

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