—COVID-19神経合併症（5）—嗅覚・味覚障害update

Smell and Taste Dysfunctions owing to COVID-19

嗅覚・味覚障害は新型コロナウイルス感染症に特徴的な症状であるが，その発生頻度と病態はウイルス株の変異により変化を遂げた。嗅覚障害の発生には嗅上皮に存在するアンジオテンシン変換酵素2が関与している。嗅覚障害の多くは数週で改善するが，数カ月以上にわたり症状が遷延する症例では異嗅症が患者を悩ませる。嗅覚障害が遷延する症例では，障害が嗅神経細胞まで及び，嗅神経性嗅覚障害となることが推測される。

Abstract

Olfactory and taste dysfunctions are characteristic symptoms of coronavirus disease 2019 (COVID-19); however, their frequencies and pathogeneses keep changing because of rapid mutations of the viral strains. Angiotensin-converting enzyme 2, a receptor for the spike protein of SARS-CoV-2 in the olfactory epithelium, is involved in the development of olfactory dysfunction. In general, olfactory dysfunctions resolve in a few weeks. However, there are cases wherein the symptoms persist for several months or longer, and parosmia or phantosmia affects the patient's quality of life. It is also assumed that the damage owing to COVID-19 extends to olfactory nerve cells, resulting in sensorineural olfactory dysfunction similar to post-infectious olfactory dysfunction.