Relative mRNA expression of MUC1 (A), MUC4 (B), MUC13 (C), MUC16 (D), MUC20 (E), MUC21 (F), MUC2 (G), MUC5AC (H), MUC5B (I), and MUC6 (J) in critically ill COVID-19 (n = 50), mild COVID-19 (n = 35), mild non–COVID-19 (n = 30) and healthy controls (n = 20). Data are presented as mean ± SEM. Each filled circle in the dot plots represents a patient and a blue filled circle with a cross (n = 14), as shown for MUC1, denotes deceased patients in the critically ill COVID-19 group. Significant differences between critically ill COVID-19, mild COVID-19, and non–COVID-19 patients and healthy controls as well as among the patient groups are indicated by a P value. One-way ANOVA, Tukey’s post hoc multiple-comparison test.