Abstract
A recent letter published in the Ear, Nose & Throat Journal called attention to the hypothesis that the xerostomia reported in patients with the Coronavirus Disease 2019 (COVID-19) occurs due to the neuroinvasive and neurotropism potential of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In fact, angiotensin-converting enzyme 2 (ACE-2), the main site of entry of SARS-CoV-2 into the cell, was found to be present in the ductal elements of salivary gland and several other tissues. However, some points are worth to be addressed.
We read with great interest the article of Saniasiaya 1 published in the Ear, Nose & Throat Journal. The author called attention to the hypothesis that the xerostomia reported in patients with the Coronavirus Disease 2019 (COVID-19) occurs due to the neuroinvasive and neurotropism potential of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In fact, angiotensin-converting enzyme 2 (ACE-2), reported to be the main site of entry of SARS-CoV-2 into the cell, was found to be present in the ductal elements of the salivary glands 2 and several other tissues. This reinforces the possibility of salivary gland infection. 3,4 However, some points regarding the xerostomia and also the taste alterations reported in COVID-19 patients are worth to be addressed.
Even though the mechanism behind the quantitative and qualitative alterations in saliva of COVID-19 patient is still unclear, 5 the effect of the SARS-CoV-2 infection in the salivary glands is believed to contribute to explain these alterations. 3,6 It is worth to note, however, that the reported taste disturbances in patients with COVID-19 have only been subjective in nature, and it is not quite clear if these patients experience disturbances in their sense of taste or whether they are experiencing disturbances in flavor 3 .
It has been hypothesized that SARS-CoV-2 may alter the cells and circuits involved in chemosensory processing and thereby lead to disturbances in taste and smell. 5 Even though, local renin–angiotensin system, which is linked to ACE-2, might be involved in the modulating the activity of taste cells, 7 there is evidence that SARS-CoV-2 infection to taste bud cells might not be the cause of taste loss in patients with COVID-19. 8 Besides, it has been also hypothesized that alterations in saliva composition and flow could be directly or indirectly caused by SARS-CoV-2 infection in salivary glands could. 3,6 This might lead to both xerostomia and taste alterations. Overall, studies are still necessary to unveil the precise pathophysiological mechanism by which SARS-CoV-2 causes the reported xerostomia and taste disturbances.
