Phoenixin-14 May Be a Potential Limiting Neuropeptide for Exaggerated Inflammation in Familial Mediterranean Fever and Periodic Fever, Aphthous Stomatitis, Pharyngitis and Cervical Adenitis Syndrome: A Comparative Study.

OBJECTIVE: This study aimed to evaluate serum Phoenixin-14 (PNX-14) levels in Familial Mediterranean Fever (FMF) and Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Cervical Adenitis (PFAPA) patients during both attack and attack-free periods to investigate its potential biomarker value. METHODS: A total of 140 children were included in this cross-sectional study: 46 FMF, 48 PFAPA, and 46 healthy children. Blood samples were collected during both febrile and attack-free periods in the FMF and PFAPA patients, whereas samples from healthy controls were collected at a single time point. C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), serum amyloid A (SAA), fibrinogen, and serum PNX-14 levels were evaluated. Serum PNX-14 levels were measured using ELISA. SPSS 25 was used for statistical analyses. RESULTS: PNX-14 levels were significantly higher during attack periods in FMF and PFAPA patients compared to attack-free periods and healthy controls (p < 0.001). PNX-14 levels during attack-free periods were also higher in both patient groups than in healthy controls (p < 0.001). While a positive correlation was observed between PNX-14 levels and CRP (rho = 0.222, p = 0.04), no significant correlation was observed with ESR, SAA, or fibrinogen. No significant associations were observed between PNX-14 levels and disease severity (PRAS), colchicine treatment duration, or daily colchicine dose in the FMF group. CONCLUSION: PNX-14 may be part of a neuroimmune response aimed at resolving inflammation in autoinflammatory processes and could be a potential immunomodulatory biomarker. PNX-14 may be a complementary indicator reflecting inflammatory burden or the healing process.