The “X factor” researchers have been looking for was the X chromosome all along.
As early as April, a strange pattern began to emerge in the data of coronavirus death rates: in some places, men appeared to be dying from COVID-19 at twice the rate of women. This fact has puzzled doctors and statisticians, inspiring research into the social and biological factors that might cause such a disparity. This week, a new study published in the medical journal JAMA suggests one possible explanation: men may be prone to more severe effects of COVID due to higher rates of genetic defects.
The study probed the cases of four coronavirus patients—two sets of brothers from unrelated families in the Netherlands—who were all admitted to the ICU with severe symptoms of the virus. According to the researchers, these subjects were selected because “in severely affected young men, and in particular in brother pairs (sharing half of their genomes, with an increased chance of identifying an X-linked disease), a unique genetic defect might be present that could indicate a genetic predisposition to contract coronavirus infections.”
Using genetic sequencing and immunological tests, the researchers indeed identified rare genetic defects on the X chromosomes of the subjects. They determined that these defects contributed to their severe cases by dramatically weakening the subjects’ immune responses (one of the four young men ultimately died of his condition).
Though the subjects’ particular defects are too rare to account for the broader sex-based disparity in patient outcomes, they do suggest that genetic variation may play a wider role in men’s higher COVID-related death rates. Notably, men have one copy of the X chromosome, while women have two. Many researchers have concluded that this gives women a genetic advantage over men by lowering a woman’s chances of serious illness if at least one of the two chromosomes is healthy.
Though a study of four cases is hardly exhaustive, it opens the door to further research on the subject of how genetic factors influence case severity and patient outcomes when it comes to coronavirus. Ultimately, this may help shed some light on why otherwise healthy young men are falling dangerously ill, and point to new treatments that could save countless lives. And for more factors that influence patient outcomes, read up on the 4 Coronavirus Symptoms Most Likely to Be Deadly.