A clinical study showed that loss-of-function variants in X-linked TLR7 genes were associated with impaired type I and II IFN responses in young males, suggesting that the difference in TLR7 gene dosage between males and females could explain, at least in part, the predisposition of males to developing severe COVID-19 (van der Made et al., 2020). The gene discussed is TLR7; the disease is COVID-19.