A. Lovato, A. Antonini, C. de Filippis
Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery, 2020
To the Editor: We read with interest the recent systematic review and meta-analysis by Tong et al that investigated the prevalence of olfactory and gustatory dysfunction in patients with COVID-19. In our opinion, the authors should have discussed 2 additional points. First of all, Tong and colleagues found only 1 Asian study reporting a few cases of olfactory and taste alterations (5%), and they did not discuss this evident difference between Chinese and other reports. Many Iranian, European, and American patients with COVID-19 experienced anosmia and/or hypogeusia, but these symptoms were anecdotal in Chinese case series. Most of the Asian studies included hospitalized patients who were probably more affected by the disease (moderate to severe cases), while preliminary evidence supported the fact that olfactory and taste dysfunctions could be more frequent in mild to moderate cases of COVID-19. However, this seemed insufficient to explain the different prevalence of these complaints between American/European and Chinese patients with COVID-19. The differences between the world regions, especially in terms of olfactory and gustatory dysfunctions, could be related to variations in the genetic pattern of SARS-CoV-2 (potential mutations). Another possible explanation could be related to the well-established polymorphism in ACE2 expression (angiotensin converting enzyme 2; ie, the receptor of SARS-CoV-2) in the human tissues. In fact, different ACE2 polymorphisms and expression levels have been found between Asian and European populations. Second and more important, Tong and colleagues should have discussed the clinical course of olfactory and gustatory disorders in COVID-19. Recently, we participated in a multicenter European study recruiting 417 patients with mild to moderate cases of COVID-19, which was included in the Tong et al meta-analysis: .80% reported olfactory and taste alterations, and anosmia was the initial presenting symptom in 11.8% of cases. Furthermore, we found that olfactory dysfunction persisted in 56% of cases 14 days after general symptoms resolution. Similarly, Vaira et al, considering 72 COVID-19 cases, found in 34% a persistence of alterations in taste and olfaction. Previous studies have already shown the ability of SARS coronavirus to cause neuronal death in mice by invading the brain via the nose close to the olfactory epithelium. Growing evidence is suggesting that smell and taste disorders may be persistent in some patients with COVID-19. There is an urgent need for randomized controlled clinical trials focused on treatment of COVID-19 olfactory and taste alterations.
Cited by 5 publications.
Field of study: Medicine