Case series/case reports (Indigo)
Anosmia, the loss of smell, is a common and often the sole symptom of COVID-19. The onset of the sequence of pathobiological events leading to olfactory dysfunction remains obscure. In this article the authors have developed a postmortem bedside surgical procedure to harvest endoscopically samples of respiratory and olfactory mucosae and whole olfactory bulbs. Their cohort of 85 cases included COVID-19 patients who died a few days after infection with SARS-CoV-2, enabling the possibility to catch the virus while it was still replicating. The authors found that sustentacular cells are the major target cell type in the olfactory mucosa. They failed to find evidence for infection of olfactory sensory neurons, and the parenchyma of the olfactory bulb is spared as well. Thus, SARS-CoV-2 does not appear to be a neurotropic virus. The authors concluded that transient insufficient support from sustentacular cells triggers transient olfactory dysfunction in COVID-19. Olfactory sensory neurons would become affected without getting infected.
Khan M, Yoo SJ, Clijsters M, Backaert W, Vanstapel A, Speleman K, Lietaer C, Choi S, Hether TD, Marcelis L, Nam A, Pan L, Reeves JW, Van Bulck P, Zhou H, Bourgeois M, Debaveye Y, De Munter P, Gunst J, Jorissen M, Lagrou K, Lorent N, Neyrinck A, Peetermans M, Thal DR, Vandenbriele C, Wauters J, Mombaerts P, Van Gerven L. Visualizing in deceased COVID-19 patients how SARS-CoV-2 attacks the respiratory and olfactory mucosae but spares the olfactory bulb. Cell. 2021 Nov 3:S0092-8674(21)01282-4. doi: 10.1016/j.cell.2021.10.027.