¹Ondokuz Mayıs University, Faculty of Veterinary Medicine, Internal Medicine Department, TR-55200 Samsun - TÜRKİYE DOI : 10.9775/kvfd.2026.37010 This study aimed to evaluate serum matrix metalloproteinase-9 (MMP-9), interleukin-8 (IL-8), and hematology-derived inflammatory indices as potential prognostic markers in cats with FIP, with particular emphasis on seizure activity. Forty-eight client-owned cats diagnosed with FIP and 14 healthy control cats were included. Cats with FIP were categorized into three groups: effusive FIP (EFIP, n=11), non-effusive FIP (NFIP, n=30), and non-effusive FIP with seizures (NFIP-S, n=7). Hematological parameters were analyzed to calculate inflammatory indices including dLNR, SIRI, AISI, SII, NLR, and related ratios. Serum MMP-9 and IL-8 concentrations were measured using ELISA. Serum MMP-9 concentrations were significantly higher in cats with NFIP-S group compared with other groups (P<0.05). IL-8 levels were higher in the seizure group but did not differ significantly between groups. Hematology-derived inflammatory indices were significantly elevated in EFIP and NFIP groups compared with controls (P<0.05), whereas NFIP-S group showed values comparable to controls. MMP-9 levels were positively correlated with IL-8 (Spearman"s ρ=0.44, P=0.001). MMP-9 levels were significantly associated with seizure occurrence (OR=1.13, P=0.016). Survival analysis demonstrated significantly shorter survival in the NFIP-S group (P=0.042). Elevated serum MMP-9 in cats with non-effusive FIP and seizures suggests a potential role of MMP-9 mediated blood-brain barrier disruption and neuroinflammation in seizure pathogenesis. MMP-9 may serve as a useful biomarker for neurological involvement and prognosis in FIP. Keywords : Feline infectious peritonitis, MMP-9, IL-8, Seizure, Neuroinflammation, Blood-brain barrier