Abstract
Ever since severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was discovered, new findings are emerging linking to this deadly pandemic which causes coronavirus disease 2019 (COVID-19). Novel clinical manifestations are being unraveled on a daily basis although World Health Organization strongly supports acute respiratory illness, fever, and cough to be the most prominent clinical manifestation. 1 Some symptoms may not be so blatant and are prone to be overlooked even by adept physicians. Recently, xerostomia or dry mouth syndrome has been linked with COVID-19 as xerostomia has been found largely amongst COVID-19 patients. 2 Dry mouth or xerostomia is a sign of dehydration which could occur secondary to underlying illness such as COVID-19.
We hypothesize that xerostomia occurs due to the neuroinvasive and neurotropism potential of SARS-CoV-2. Angiotensin-converting enzyme 2 (ACE2) has been reported to be the main site of entry of SARS-CoV-2 into the cell. Additionally, the pathway of entry of SARS-COV-2 into the peripheral nervous system and central nervous system through synaptic contact has been postulated. 3
Dysgeusia, one of the newly discovered COVID-19 clinical manifestation, is thought to occur secondary to xerostomia. Alteration in the quantity and composition of saliva causing gustatory dysfunction 4 supports the notion that xerostomia could cause gustatory dysfunction. In the same vein, reduction of proteins as well as antiviral properties within the saliva could be an indicator of COVID-19. 5
Study by Biadsee et al found 72 of their COVID-19 patients complained of xerostomia which reported a strong association with gustatory dysfunction and burning mouth. 6 Traditionally, mouth breathing which occurs secondary to viral-induced nasal obstruction and rhinorrhea has been considered the main culprit causing xerostomia. However, it is noteworthy that nasal obstruction and rhinorrhea are not the main presentation of COVID-19.
Previous study has reported on angiotensin-converting enzyme (ACE2) receptor 2 in epithelial cells of the salivary gland as the primary site for coronavirus. 7 Parallel to that, viral-induced infection and inflammation is a known cause of xerostomia. Hence, we would like to highlight that xerostomia ought to be considered as a possible clinical manifestation of COVID-19.
