Smell and taste disorders in COVID-19: From pathogenesis to clinical features and outcomes

Abstract

Patients with COVID-19 often complain of smell and taste disorders (STD). STD emerge early in the course of the disease, seem to be more common in SARS-CoV-2 infection than in other upper respiratory tract infection, and could in some cases persist for long after resolution of respiratory symptoms. Current evidence suggests that STD probably result from a loss of function of olfactory sensory neurons and taste buds, mainly caused by infection, inflammation, and subsequent dysfunction of supporting non-neuronal cells in the mucosa. However, the possible occurrence of other mechanisms leading to chemosensory dysfunction has also been hypothesized, and contrasting data have been reported regarding the direct infection of sensory neurons by SARS-CoV-2. In this mini-review, we summarize the currently available literature on pathogenesis, clinical manifestations, diagnosis, and outcomes of STD in COVID-19 and discuss possible future directions of research on this topic.

eVITTA: a web-based visualization and inference toolbox for transcriptome analysis

“…At the gene level, key olfactory transducers, including G protein subunit alpha L ( GNAL ) ( 38 ) and cyclic nucleotide-gated channel subunit alpha 4 ( CNGA4 ) ( 39 ), showed reduced expression (Figure 2C , D , Supplementary Figure S2B ). The observation of deregulated olfactory signaling during SARS-CoV-2 infection agrees well with the clinical presentation of anosmia in COVID-19 cases ( 40 ) and with a recent report of transient olfactory dysfunction in mice infected with SARS-CoV-2 ( 41 ). Together, this demonstrates eVITTA’s capacity to capture both broad and granular patterns in gene expression, which facilitates the identification of biological insights.…”

Clinical Features of Olfactory Dysfunction in COVID-19 Patients

“…To date, several studies have evaluated the clinical features and pathophysiology of COVID-19 infection-associated OD. Mastrangelo et al 17 reported that COVID-19 infection-associated OD occurred without nasal congestion or discharge. These clinical features suggest that OD might be caused by sensorineural damage.…”

“…Moreover, they suggested that phagocytes infection and vascular damage in olfactory bulb, and infection and death of supporting cells due to COVID-19 lead to inflammatory cytokine release and causes neuronal dysfunction. 17 Lv et al 18 performed the telephone survey in 196 patients and reported that impaired olfaction in the COVID-19 patients was restored in 89.7% of the patients within 3 months of their discharge from hospital. Brandão Neto et al 19 also performed a telephone survey using 11-point category rating scale in 655 patients who recovered from COVID-19 infection.…”

Covi̇d 19 Hastalarinda Tat Ve Koku Bozukluklari

“…Ayrıca koku bozukluğunun anatomik yerleşimine göre de iletim tipi koku bozuklukları ve sensörinöral koku bozuklukları olarak iki grupta da incelenebilir. Olfaktör sinire kadar olan yoldaki patolojiler iletim tipi koku bozukluğuna yol açarken olfaktör sinir ve merkezi sinir sistemindeki patolojiler ise sensörinöral koku bozukluklarına yol açmaktadır (10). En sık suçlanan iki koku kaybı mekanizması ise sinonazal inflamasyon, sekresyon, ödem veya tümöral nedenlere bağlı kokunun olfaktör bölgeye ulaşmasını önleyen nazal obstuksiyon ve olfaktör nöroepitelin dejenerasyonudur (12).…”

“…Bazı hastalarda tat ve koku alamama şikayetlerinden uzun süre sonra ortaya çıkan parosmi (ortamda var olan kokudan farklı bir koku algılama durumudur), fantosmi (koku uyaranı yokken koku alma durumudur) gibi koku bozukluklarının nedeni ise tekrar oluşmakta olan sinir ağlarının yeterince olgunlaşmamış dokular olmasına bağlanmaktadır (10).…”