DIAGNOSTIC VALUE OF SERUM MMP-9 AND GRANZYME B IN BULLOUS PEMPHIGOID: A CASE–CONTROL STUDY

Abstract

Background: Bullous pemphigoid (BP) is a common autoimmune blistering disease in the elderly. Proteases like matrix metalloproteinase-9 (MMP-9) and granzyme B contribute to dermal–epidermal separation, but their circulating levels and clinical relevance remain unclear. Objectives: To compare serum levels of MMP-9 and granzyme B in BP patients versus healthy controls, and evaluate their correlations with disease severity and clinical features. Methods: This single-center case–control study in Hanoi, Vietnam (June 2024–June 2025) included 17 newly diagnosed BP patients and 17 age-matched healthy controls. Serum MMP-9 and granzyme B were measured by ELISA and normalized to total protein. Clinical parameters including BPDAI scores were recorded. Associations and diagnostic value were assessed using correlation and ROC analysis. Results: Serum MMP-9 levels were significantly lower in BP than controls (median 375.2 vs. 728.1 pg/µg protein; p = 0.0376), while granzyme B levels were higher but not statistically significant (p = 0.454). MMP-9 positively correlated with BPDAI (r = 0.47, p = 0.03), unlike granzyme B. MMP-9 and granzyme B showed moderate correlation (r = 0.66, p = 0.002). BP patients with diabetes had higher levels of both markers. Combining MMP-9 and granzyme B improved diagnostic accuracy (AUC = 0.844). Conclusions: Circulating MMP-9 levels are reduced in BP patients but correlate with disease severity. Granzyme B alone has limited value. Combined measurement enhances diagnostic performance and may aid in disease monitoring.