An X-linked deleterious variant of TLR7 is reported to cause loss of function in male patients with COVID-19, which resulted in low levels of type I IFN by plasmacytoid DCs, leading to an impairment of type I interferon in response to SARS-CoV-2 infection, demonstrating the importance of functional TLR7 in regulating the progression and severity of COVID-19 (136). Here, TLR7 is linked to COVID-19.