1/7 TLR7 loss-of-functions mutations can lead to an immunodeficiency with a strong predisposition to develop a severe form of COVID-19 in young male patients. jamanetwork.com/journals/jama/…2/7 As such, this is the first description of a monogenic risk factor related to COVID-19 and a first risk factor next to the known general risk factors (age, male sex, cardiovascular disease, chronic disease, obesity).