To further characterize patients with IgG/IgA pemphigus and to differentiate them from those with conventional pemphigus, IHC staining of potential biomarkers, including C5a, CD89, IL-8, MPO, MMP-9, and IL-17, was performed with specimens from all IgG/IgA pemphigus cases (N = 22) and all conventional pemphigus controls (N = 20) (Figure 3a). This evidence concerns the gene MMP9 and pemphigus.