We noticed that mucus plugs from patients with both asthma and COPD were tethered to the surface of goblet cells by mucin strands that connected the edge of the mucus plug to the epithelium (Figure 2L and Supplemental Figure 1, A and B; supplemental material available online with this article; https://doi.org/10.1172/JCI186889DS1). This evidence concerns the gene MUC5AC and asthma.