A few studies investigating a small number of patients have reported aberrant expression of several mucins, including MUC2, MUC4, MUC5AC, MUC5B, MUC6, MUC13, MUC16, and MUC20, in the mucus or BALF of severely ill patients with COVID-19 (9–11). This evidence concerns the gene MUC4 and COVID-19.