Since 2019, Coronavirus Disease 2019(COVID-19) has affected millions of people worldwide. Except for acute respiratory distress syndrome, dysgeusis is also a common symptom of COVID-19 that burdens patients for weeks or permanently. However, the mechanisms underlying taste dysfunctions remain unclear. Here, we performed complete autopsies of five patients who died of COVID-19. Integrated tongue samples, including numerous taste buds, salivary glands, vessels, and nerves were collected to map the pathology, distribution, cell tropism, and receptor distribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the tongue. Our results revealed that all patients had moderate lymphocyte infiltration around the salivary glands and in the lamina propria adjacent to the mucosa, and pyknosis in the epithelia of taste buds and salivary glands. This may be because the serous acini, salivary gland ducts, and taste buds are the primary sites of SARS-CoV-2 infection. Multicolor immunofluorescence showed that SARS-CoV-2 readily infects Keratin (KRT)7+ taste receptor cells in taste buds, secretory cells in serous acini, and inner epithelial cells in the ducts. The major receptors, angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine subtype 2 (TMPRSS2), were both abundantly expressed in these cells. Viral antigens and receptor were both rarely detected in vessels and nerves. This indicates that SARS-CoV-2 infection triggers pathological injury in the tongue, and that dysgeusis may be directly related to viral infection and cellular damage.

BACKGROUND: Among all studies describing COVID-19 clinical features during the first wave of the pandemic, only a few retrospective studies have assessed the correlation between olfac-tory dysfunction (OD) and the evolution of disease severity. The main aim was to assess whether OD is a predictive factor of COVID-19 severity based on the patient\'s medical management (outpa-tient care, standard hospital admission, and ICU admission).
METHODS: A national, prospective, mul-ticenter cohort study was conducted in 20 public hospitals and a public center for COVID-19 screen-ing. During the first wave of the pandemic, from 6 April to 11 May 2020, all patients tested positive for COVID-19 confirmed by RT-PCR underwent two follow-up ENT consultations within 10 days of symptom onset. The main outcome measures were the evolution of medical management (out-patient care, standard hospital admission, and ICU admission) at diagnosis and along the clinical course of COVID-19 disease.
RESULTS: Among 481 patients included, the prevalence of OD was 60.7%, and it affected mostly female patients (74.3%) under 65 years old (92.5%), with fewer comor-bidities than patients with normal olfactory function. Here, 99.3% (290/292) of patients with OD presented with non-severe COVID-19 disease. Patients reporting OD were significantly less hospi-talized than the ones managed as outpatients, in either a standard medical unit or an ICU. Conclu-sions: As regards the clinical course of COVID-19 disease, OD could predict a decreased risk of hospitalization during the first wave of the pandemic.

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Emerging data suggest an increasing prevalence of persistent symptoms in individuals affected by coronavirus disease-19 (COVID-19). The objective of this study was to determine the relative frequency of altered taste and smell in COVID reinfection (multiple COVID positive tests) and long COVID (one COVID positive test). We sent an electronic survey to patients in the Indiana University Health COVID registry with positive COVID test results, querying if they were experiencing symptoms consistent with long COVID including altered chemosensory perceptions. Among the 225 respondents, a greater long COVID burden and COVID reinfection was observed in women. Joint pain was reported as the most common symptom experienced by 18% of individuals in the long COVID cohort. In the COVID reinfection cohort >20% of individuals reported headache, joint pain, and cough. Taste perception worse than pre-COVID was reported by 29% and 42% of individuals in the long COVID and COVID reinfection cohorts, respectively. Smell perception worse than pre-COVID was reported by 37% and 46% of individuals in long COVID and COVID reinfection cohorts, respectively. Further, Chi-square test suggested significant association between pre-COVID severity of taste/smell perception and headache in both cohorts. Our findings highlight the prevalence of persistent chemosensory dysfunction for two years and longer in long COVID and COVID reinfection.

Electrogustometry (EGM) is a practical way to test taste. It is typically performed using unipolar electrodes, with the anode on the tongue and the cathode on the hand, forearm, or neck. This results in electric current passing through nontaste tissues and adds a level of impracticality to its clinical application. We compared, using a repeated measures counterbalanced design, anodal thresholds from a unipolar electrode to those of a unique bipolar electrode in which the anode and cathode are contiguously located. Both sides of the anterior tongue were assessed in 70 subjects, as were the effects of age and sex. Nonparametric analyses were performed. The median threshold of the bipolar electrode\'s central disk (2.49 µA) did not differ from that of the unipolar electrode (2.96 µA) (P = 0.84). On average, older persons exhibited higher thresholds. No significant sex or tongue side effects were evident. Interestingly, when the annular (donut-shaped) bipolar electrode served as the anode, the threshold was higher than that of the other electrodes (5.19 µA; Ps < 0.001). This conceivably reflected lessened summation of activity among adjacent afferents and partial sampling of tongue regions with fewer taste buds. Correlations among all EGM thresholds were nominally higher for women than for men, ranging from 0.83 to 0.85 for women and 0.54 to 0.67 for men; all Ps < 0.001. This study validates the use of a bipolar electrode for assessing taste function, averting movement of current through nontaste-related tissues and making such testing safer and more practical.

The aim of this study was to prospectively evaluate the olfactory function in a series of individuals infected with SARS-CoV-2 and who had undergone psychophysical olfactory assessment prior to infection. Individuals unexposed to SARS-CoV-2 infection underwent a psychophysical evaluation of smell with the Sniffin\' Sticks test. The subjects were followed prospectively and included in the study if they developed SARS-CoV-2 infection with a second test 60 days after recovery. At the 60-day follow-up of the 41 included subjects, 2 (4.9%) self-reported persistent olfactory dysfunction (OD). The differences between TDI scores before and after infection were statistically significant (37 [interquartile range (IQR), 34.25-39.25] vs 34.75 [IQR, 32.25-38]; p = .021). Analyzing the individual olfactory domains, the differences were significant for threshold (T) (9.75 [IQR, 9-11.25] vs 8.25 [IQR, 7.25-10.25]; p = .009) but not for odor discrimination (D) (p = .443) and identification (I) (p = .159). SARS-CoV-2 causes a significant reduction in the olfactory function, in particular affecting the olfactory threshold, even in subjects who do not self-report an OD.

Taste dysfunction has been associated with chronic kidney disease (CKD) especially end stage kidney disease (ESKD) and also implicated as one of the predisposing factors for the prevalent malnutrition, muscle wasting and impaired quality of life among patients with CKD. To assess the taste function and determine the pattern of taste dysfunction in patients with CKD attending the University College Hospital, Ibadan. This was a cross sectional, hospital-based case-control study of adult patients with CKD. The control group were age and sex matched without CKD. Interviewer-assisted questionnaires were administered on all participants to obtain clinical information concerning demographics, clinical data on kidney disease and taste dysfunction. The four basic taste modalities namely; sweet, sour, bitter and salt taste senses of the participants were tested with validated \"taste strips\". There were 100 patients with CKD and 100 healthy controls, age ranges between 19 and 86 years (mean ± SD = 46.3 ± 13.9 years) and 20 and 85 years (mean ± SD = 43.4 ± 14.9 years), respectively. There was no statistically significant difference between cases and control gender distribution (p = 0.57). Hypogeusia was found in 27.0% of CKD patients with specific taste modalities dysfunction for salt, sour, sweet and bitter taste of 13.0, 24.0, 13.0 and 17.0%, respectively. The controls only had specific taste modalities dysfunction for salt, sour and bitter taste of 1.0% for each of the taste modalities. The mean total taste scores in the cases and controls were - 9.8 ± 3.2 and 13.4 ± 1.5 (p = 0.001), respectively. The mean taste scores were significantly lower among the cases than controls, salt taste-2.82 ± 1.1 and 3.7 ± 0.7 (p = 0.001), sour taste - 2.2 ± 1.0 and 3.2 ± 0.7 (p = 0.001), sweet taste-, 2.9 ± 1.8 and 3.8 ± 0.5 (p = 0.001), bitter taste - 1.9 ± 1.2 and 2.8 ± 0.9 (p = 0.001). Taste dysfunction is prevalent among patients with CKD and the affectation involves all taste modalities.

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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections can cause loss or alteration of taste and smell as early symptoms or sequelae, but the detailed mechanism behind this phenomenon remains unclear. Here, we investigated whether the SARS-CoV-2 spike protein induces taste cell apoptosis and expression of the apoptosis-related cytokine TNF-α in male Sprague-Dawley rats. Terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP)-fluorescein nick end labeling (TUNEL) assay results revealed a significantly higher apoptosis index for taste cells in the SARS-CoV-2 group than for those in the control group. An immunohistochemistry analysis indicated significantly more TNF-α-positive cells in the SARS-CoV-2 group compared with the control group. These data suggest that the SARS-CoV-2 spike protein promotes taste cell apoptosis and the release of apoptosis-related cytokine TNF-α, implicating its contribution to the taste malfunction caused by coronavirus disease 2019 (COVID-19).

BACKGROUND: It is plausible that immunopathological processes associated with psoriasis might contribute to the occurrence of olfactory or taste dysfunction. However, the actual association was still unknown.
OBJECTIVE: To determine the relationship between olfactory or taste dysfunction and psoriasis.
METHODS: Two cross-sectional studies were performed by using National Health and Nutrition Examination Survey (NHANES) data. Participants with psoriasis were defined as cases and those without psoriasis were identified as controls. Taste and smell self-reported questionnaires were used to define smell/taste alterations and identification tests were used to assure the smell/taste dysfunctions. Logistic regression models with inverse probability treatment weighting (IPTW) strategies were conducted to investigated the relationship between psoriasis and olfactory or taste dysfunction.
RESULTS: Self-reported questionnaires indicated that psoriasis patients were more likely to have perceived taste alteration (IPTW-aOR = 1.43) and smell alteration (IPTW-aOR = 1.22). Identification tests revealed that psoriasis was associated with taste dysfunction (IPTW-aOR = 1.28) and olfactory dysfunction (IPTW-aOR = 1.22). Relevant findings showed that psoriasis may be significantly associated with taste or olfactory dysfunction regardless of the questionnaire data or identification examination data used.
CONCLUSIONS: Olfactory and taste dysfunction could be considered comorbidities in patients with psoriasis based on our observational study. Therefore, physicians should be cautious of olfaction and taste alterations among patients with psoriasis.