Pathogenesis of taste impairment and salivary dysfunction in COVID-19 patients.

Coronavirus disease 2019 (COVID-19) is a highly transmissible pandemic disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The characteristics of the disease include a broad range of symptoms from mild to serious to death, with mild pneumonia to acute respiratory distress syndrome and complications in extrapulmonary organs. Taste impairment and salivary dysfunction are common early symptoms in COVID-19 patients. The mouth is a significant entry route for SARS-COV-2, similar to the nose and eyes. The cells of the oral epithelium, taste buds, and minor and major salivary glands express cell entry factors for SARS-COV-2, such as ACE2, TMPRSS2, and Furin. We describe the occurrence of taste impairment and salivary dysfunction in COVID-19 patients and show immunohistochemical findings regarding the cell entry factors in the oral tissue. We review and describe the pathogeneses of taste impairment and salivary dysfunction. Treatment for the oral disease is also described. Recently, it was reported that some people experience persistent and prolonged taste impairment and salivary dysfunction, described as post-COVID-19 syndrome or long COVID-19, after the acute illness of the infection has healed. To resolve these problems, it is important to understand the pathogenesis of oral complications. Recently, important advances have been reported in the understanding of gustatory impairment and salivary dysfunction. Although some progress has been made, considerable effort is still required for in-depth elucidation of the pathogenesis.

Reversible Taste Loss in a COVID-19 Patient With Preexisting Chronic Smell Impairment.

Smell loss is important for coronavirus disease-2019 (COVID-19) screening and diagnosis. Particular attention should be paid to individuals with pre-COVID-19 chronic hyposmia or anosmia. We report a case of reversible taste impairment in a COVID-19 patient with chronically impaired sense of smell. This case emphasizes the importance of COVID-19-related taste assessment.

Neurological and Musculoskeletal Features of COVID-19: A Systematic Review and Meta-Analysis.

Importance: Some of the symptoms of COVID-19 are fever, cough, and breathing difficulty. However, the mechanism of the disease, including some of the symptoms such as the neurological and musculoskeletal symptoms, is still poorly understood. Objective: The aim of this review is to summarize the evidence on the neurological and musculoskeletal symptoms of the disease. This may help with early diagnosis, prevention of disease spread, and treatment planning. Data Sources: MEDLINE, EMBASE, Web of Science, and Google Scholar (first 100 hits) were searched until April 17, 2020. The key search terms used were "coronavirus" and "signs and symptoms." Only studies written in English were included. Study Selection: The selection was performed by two independent reviewers using EndNote and Rayyan software. Any disagreement was resolved by consensus or by a third reviewer. Data Extraction and Synthesis: PRISMA guidelines were followed for abstracting data and assessing the quality of the studies. These were carried out by two and three independent reviewers, respectively. Any disagreement was resolved by consensus or by a third reviewer. The data were analyzed using qualitative synthesis and pooled using a random-effect model. Main Outcome(s) and Measure(s): The outcomes in the study include country, study design, participant details (sex, age, sample size), and neurological and musculoskeletal features. Result: Sixty studies (n = 11, 069) were included in the review, and 51 studies were used in the meta-analysis. The median or mean age ranged from 24 to 95 years. The prevalence of neurological and musculoskeletal manifestations was 35% for smell impairment (95% CI 0-94%; I 2 99.63%), 33% for taste impairment (95% CI 0-91%; I 2 99.58%), 19% for myalgia (95% CI 16-23; I 2 95%), 12% for headache (95% CI 9-15; I 2 93.12%), 10% for back pain (95% CI 1-23%; I 2 80.20%), 10% for dizziness (95% CI 3-19%; I 2 86.74%), 3% for acute cerebrovascular disease (95% CI 1-5%; I 2 0%), and 2% for impaired consciousness (95% CI 1-2%; I 2 0%). Conclusion and Relevance: Patients with COVID-19 present with neurological and musculoskeletal symptoms. Therefore, clinicians need to be vigilant in the diagnosis and treatment of these patients.