Using deep sequencing methods, researchers have identified differences in the nasal microbial composition of patients with granulomatosis with polyangiitis (GPA) compared with that in healthy individuals, including a decreased relative abundance of Propionibacterium acnes and Staphylococcus epidermidis. In patients with GPA, the use of non-glucocorticoid immunosuppressive therapy was associated with a healthy nasal bacterial composition, whereas disease activity was associated with an altered nasal mycobiota, including a decreased relative abundance of the order Malasseziales in patients with active disease compared with patients in remission.