SERPINA4 encodes kallistatin, a serine protease inhibitor that functions as an anti-inflammatory and anti-angiogenic protein. The protein primarily inhibits tissue kallikrein activity through formation of stable enzyme-inhibitor complexes [UniProt]. SERPINA4 demonstrates protective roles in multiple disease contexts. In cardiovascular disease, kallistatin shows anti-inflammatory properties and correlates with abdominal aortic aneurysm pathogenesis, where decreased levels represent increased rupture risk 1. The protein also functions as a potential biomarker for organ dysfunction - reduced plasma levels correlate with chr14 liver disease severity 2, while urinary SERPINA4 levels combined with other markers show diagnostic utility for diabetic kidney disease 3. Genetic variants in SERPINA4 demonstrate clinical significance across multiple conditions. The rs2093266 polymorphism associates with increased susceptibility to idiopathic nephrotic syndrome in children and correlates with steroid resistance, suggesting potential therapeutic targeting opportunities 4. This same variant, along with rs1955656 in SERPINA5, associates with severe acute kidney injury development in critically ill patients with septic shock 5. Additionally, SERPINA4 levels predict longitudinal visuospatial cognitive decline over 9-year follow-up 6. These findings establish SERPINA4 as a multifunctional protein with roles in inflammation, angiogenesis regulation, and potential clinical applications as both biomarker and therapeutic target.