We used histology and confocal imaging to characterize the mucin protein profile and histologic features of plugged and unplugged airways from patients with asthma (103 airways), patients with COPD (50 airways, disease control), and age-matched lung disease–free individuals acting as controls (lung disease–free control) airways (48 airways) (Figure 1). Here, MUC5AC is linked to chronic obstructive pulmonary disease.