Genetics: Genetic risk factor for COVID-19-related loss of smell or taste identified

A genetic risk factor that influences whether an individual is likely to experience a loss of smell or taste as symptoms of COVID-19 is revealed in a paper published in Nature Genetics. The genetic locus — situated near two genes, UGT2A1 and UGT2A2 — is associated with an 11% increase in the chance of developing either of these symptoms following SARS-CoV-2 infection.

Loss of smell or taste are distinctive symptoms of COVID-19; however, not all individuals infected with SARS-CoV-2 experience them, with the mechanisms responsible unclear.

Adam Auton and colleagues performed a genome-wide association study using online survey data collected from 69,841 (63% female; 37% male) research participants aged over 18 years, living in the United States or the United Kingdom. The authors found that a set of variants located near the two genes UGT2A1 and UGT2A2 increased the likelihood that an individual will experience a loss of smell or taste following SARS-CoV-2 infection by 11%. Both genes encode enzymes that are expressed in cells that line the inside of the nose and are involved in eliminating odorants that bind to receptors involved in smell detection.

This discovery provides clues into the biological mechanisms that underlie COVID-19-related loss of smell or taste. The authors caution, however, that despite a large sample size, the study is biased towards individuals of European ancestry. Distinction must also be made between loss of taste and loss of smell, which were combined in a single survey question herein. Potential clinical replication — rather than relying on self-reported symptoms — could also be beneficial, they conclude.