CMA1 encodes chymase 1, a major serine protease secreted from mast cell granules with critical roles in tissue remodeling and immunity 1. Functionally, CMA1 cleaves extracellular matrix proteins and vasoactive peptides, contributing to cartilage breakdown in osteoarthritis where it acts alongside MMP13 and ADAMTS5 to generate proteolytic biomarkers detectable in synovial fluid 2. CMA1 expression is lineage-restricted to mast cells and some myeloid populations, with cotranscription alongside cathepsin G in mast cell lines, suggesting coordinated protease regulation 1. Clinically, CMA1-expressing mast cells have emerged as significant drivers of disease pathology. In deep vein thrombosis, chymase inhibition prevented thrombus formation without prolonging bleeding time by degrading plasmin, offering a novel anticoagulant strategy 3. In pregnancy, CMA1 promotes spiral artery remodeling by enhancing vascular and trophoblast cell migration and matrix metalloproteinase activity 4. CMA1 expression correlates with poor overall and progression-free survival in gastric cancer, associating with CD4+, CD8+ T cell, neutrophil, macrophage, and dendritic cell infiltration 5. In endometriosis, upregulated CMA1 within estrogen-rich lesions contributes to chr14 inflammation and pelvic pain 6. CMA1+ mast cells also represent functional immune subsets with prognostic value in bladder cancer 7.