Pathogenesis and progression of anosmia and dysgeusia during the COVID-19 pandemic

Abstract

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is the causative agent of COVID-19 which was detected in late 2019 in Wuhan, China. As of September 2022, there have been over 612 million confirmed cases of COVID-19 with over 6.5 million associated deaths. In many cases, anosmia and dysgeusia have been identified as primary symptoms of COVID-19 infection in patients. While the loss of smell (anosmia) and loss of taste (dysgeusia) due to COVID-19 infection is transient in most patients, many report that these symptoms persist following recovery. Understanding the pathogenesis of these symptoms is paramount to early treatment of the infection. We conducted a literature review of Google Scholar and PubMed to find and analyze studies discussing anosmia and dysgeusia in the context of COVID-19 to understand the progression and management of these symptoms. The mechanism for dysgeusia is largely unknown; however, pathogenesis of anosmia includes inflammation and cytokine release resulting from the infection that alters neuronal signaling, thus inducing the loss of smell that patients experience. Anosmia may be managed and potentially resolved sooner with a combination therapy of olfactory training and budesonide irrigation of the nasal cavity. It is important to note that the variants of SARS-CoV-2 are genetically distinguished from the original virion due to a mutation in their spike proteins, giving them a different symptom profile regarding anosmia and dysgeusia. This variability in symptomatology is an area of study that needs to be further explored.

Case report: Dysgeusia in a senile male systemic lupus erythematosus patient with serious cytomegalovirus infection

“…Several hypotheses have been reported to explain its pathogenesis, including direct toxicity to taste buds, peripheral neurotropism of SARS-CoV-2, or loss of chemosensory function. 4,5 In our case, severe dysgeusia with poor intake was found after discharge from the district hospital.…”

Detection of SARS-CoV-2 IgG antibodies and inflammatory cytokines in saliva-a pilot study

“…Loss of taste and Xerostomia usually recovers 1–3 weeks after COVID-19 infection. 31 , 32 In our study due to the limitation of seeing COVID-19 positive infected patients at the hospital at that time for non-emergency care, the average duration from COVID-19 diagnosis and 1st study visit was 5.7 weeks. Therefore, the patients reporting xerostomia and loss of taste at their baseline visit were on average almost 6 weeks after initial diagnosis and maybe be suffering from longer lasting form of covid induced xerostomia and loss of taste than the Covid −19 typical patients.…”

Recovery of Smell and Taste in Patients With Persistent COVID-19-Related Hyposmia and Dysgeusia by Targeting Also Inflammation and Endothelial Dysfunction

“…We developed the treatment regimen evaluated based on a protocol used in our clinic to treat sudden sensorineural hearing loss, assuming that sensorineural conditions caused by viral infection may share common mechanisms. We also took advantage of current knowledge of the pathophysiology of SARS-CoV-2 infection, including excessive inflammatory response, edema of the infected tissues, endothelial dysfunction, and microthrombus formation, which may also play a role in the damage to the olfactory and gustatory epithelia and other relevant tissues [5,14,15,20,[23][24][25][26]. Based on this rationale, the combined regimen included a potent anti-inflammatory agent (intravenous dexamethasone followed by oral prednisone), a diuretic (acetazolamide), and an antithrombotic agent (intramuscular mesoglycan, followed by oral mesoglycan).…”

“…Since the early days of the coronavirus disease 19 (COVID-19) pandemic outbreak, several reports worldwide have described the occurrence of olfactory and gustatory dysfunction in infected patients [1,2]. These sensory symptoms were usually overlapping and appeared to occur early, before the onset of the respiratory syndrome, leading to the hypothesis that they may represent early diagnostic markers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection [2][3][4][5]. As a consequence, new-onset loss of olfaction (anosmia) and taste (ageusia) has been included by international scientific societies among the key symptoms of COVID-19.…”