TLR7 and COVID-19: However, MyD88- or IRAK-4–deficient patients with critical COVID-19 had somewhat lower blood CRP, ferritin, and LDH levels than TLR7-deficient patients with critical COVID-19 pneumonia (Asano et al., 2021), hospitalized patients under the age of 21 yr from the general population (Bourgeois et al., 2021), and patients from the general population admitted to the ICU (Pierce et al., 2020), although this difference was not statistically significant (Fig. 4, A–C).