Key proteins, elevated in severe cases, including SYND1, S100A12, HGF and CDCP1, reflect processes such as endothelial dysfunction [33,36,38,48,72,73], neutrophil activation [43,50,74,75], tissue remodeling [51,53,76,77] and systemic inflammation [54,78,79]. Here, HGF is linked to endothelial dysfunction.