Introduction: Proteinases and proteinase inhibitors have been described to play a role in autoimmune skin blistering diseases.We studied skin lesional biopsies from patients affected by several autoimmune skin blistering diseases for proteinases and proteinase inhibitors.Methods: We utilized immunohistochemistry to evaluate biopsies for α-1-antitrypsin, human matrix metalloproteinase 9 (MMP9), human tissue inhibitor of metalloproteinases 1 (TIMP-1), metallothionein and urokinase type plasminogen activator receptor (uPAR).We tested 30 patients affected by endemic pemphigus, 30 controls from the endemic area, and 15 normal controls.We also tested 30 biopsies from patients with bullous pemphigoid (BP), 20 with pemphigus vulgaris (PV), 8 with pemphigus foliaceus, and 14 with dermatitis herpetiformis (DH).Results: Contrary to findings in the current literature, most autoimmune skin blistering disease biopsies were negative for uPAR and MMP9.Only some chronic patients with El Bagre-EPF were positive to MMP9 in the dermis, in proximity to telocytes.TIMP-1 and metallothionein were positive in half of the biopsies from BP patients at the basement membrane of the skin, within several skin appendices, in areas of dermal blood vessel inflammation and within dermal mesenchymal-epithelial cell junctions.