It may not be coincidental that these 4 etiologies impair both type I and type III IFN immunity, whereas critical influenza pneumonia has only been reported in 1 of the 29 known patients with IFNAR1 or IFNAR2 deficiency (19–21, 24–33) and in none of the more than 30 patients with IL10RB deficiency (55–58). The gene discussed is IL10RB; the disease is influenza.