Effectiveness of colchicine preparation switching in pediatric colchicine-resistant familial Mediterranean fever: a real-world study.

UNLABELLED: Colchicine preparation switching is recommended before interleukin-1 (IL-1) inhibitor therapy in pediatric patients with colchicine-resistant familial Mediterranean fever (crFMF); however, real-world outcomes after switching are not well characterized. We aimed to evaluate the effectiveness of colchicine preparation switching and to compare clinical outcomes between patients managed with switching alone and those who subsequently required IL-1 inhibitor therapy. This retrospective inception cohort study included 103 pediatric crFMF patients carrying biallelic pathogenic MEFV exon 10 variants who underwent a switch from coated to compressed colchicine between August 2016 and May 2025. Clinical, laboratory, and genetic data were collected. Disease activity was assessed using the Pras score, the International Severity Scoring System for familial Mediterranean fever, and the Mor score. Patients were classified according to IL-1 inhibitor requirement; treatment escalation was the primary endpoint. Following colchicine preparation switching, attack frequency and disease activity scores decreased significantly (all p < 0.001). Sixty-three patients (61.2%) showed significant reductions in all major attack manifestations, whereas among 40 patients (38.8%) requiring IL-1 inhibitors, only fever decreased significantly (p = 0.012). CONCLUSION: Colchicine preparation switching significantly reduced attack frequency and disease activity in children with crFMF and may represent an effective intermediate therapeutic strategy before escalation to IL-1 inhibitor therapy. WHAT IS KNOWN: • Colchicine preparation switching is recommended before IL-1 inhibitor therapy in colchicine-resistant familial Mediterranean fever (crFMF), but evidence supporting this approach in children is limited. • Previous studies have reported improved disease control after switching colchicine preparations. WHAT IS NEW: • This study provides long-term pediatric data on the clinical course after colchicine preparation switching, including subsequent escalation to IL-1 inhibitor therapy. • Patients requiring subsequent IL-1 inhibitor therapy developed earlier subclinical inflammation and showed a less complete clinical response after switching.