A team of researchers, including Dr. Anna Planas from the IIBB-CSIC, has found a genetic mechanism involved in a type of exaggerated immune reaction that aggravates covid-19 in some children. This reaction is called multisystem inflammatory syndrome and, although it is rare (with a prevalence of about 1 in 10,000 infected children), it can be very serious. It usually appears four weeks after infection and causes fever, rashes, and abdominal pain. Its causes are unknown, but now researchers have studied the genetics of affected children and have found an altered genetic mechanism, they conclude in an article published in Science.