COVID-19肺外病変の画像診断―ACE2遺伝子発現率という観点から

Extrapulmonary involvement of COVID-19：imaging diagnosis with special emphasis on ACE2 gene expression

新型コロナウイルス感染症（COVID-19）が世界中で大流行している。その画像診断においては肺炎だけが着目されがちであるが，一方でCOVID-19肺炎の合併症とも称されるCOVID-19肺外病変は，時に患者の予後悪化の原因となり，また時には後遺症として患者のQOL（quality of life）を大きく左右する。本稿では全身のACE2遺伝子発現率という観点から，COVID-19の肺外病変について画像診断を主体に述べる。

COVID-19 spread all over the world becoming a pandemic illness. Although the lungs are primarily affected, SARS-CoV-2 can affect various organs. This article focuses on extrapulmonary involvement of COVID-19 with special emphasis on ACE2 expression. SARS-CoV-2 employ mechanisms for receptor recognition. The spike protein of SARS-CoV-2 binds to ACE2（angiotensin-converting enzyme 2）receptor located on the target human cell surface, which facilitates entry of the virus into various target cells/target tissues. Recent reports have revealed that not only respiratory tracts, but also cardiovascular system, alimentary tracts, hepatobiliary system, pancreas, kidneys and central nervous system are also affected in COVID-19. In these extrapulmonary involvements of COVID-19, not only direct viral infection, but also cytokine storm and coagulopathy can play important roles. Understanding of these extrapulmonary involvements is essential in the proper management of COVID-19 patients, and all radiologists should be familiar with knowledge and imaging diagnosis of these extrapulmonary involvements.