Case Report: From idiopathic recurrent pericarditis to systemic Behçet’s Disease: unmasking a unified IL-1-driven autoinflammatory phenotype

Background: Recurrent idiopathic recurrent pericarditis (RP) is increasingly recognized as an organ-specific autoinflammatory syndrome driven by the interleukin-1 (IL-1) axis. Behçet's Disease (BD), a systemic vasculitis, exhibits significant pathogenetic overlap with RP through IL-1 mediated hyperinflammation, particularly in phenotypes dominated by serositis. The clinical evolution of prolonged, seemingly idiopathic RP into overt, systemic BD upon the tapering of targeted therapy remains a critical, yet underreported, observation. Case presentation: A 42 years old female with corticosteroid-dependent, colchicine-resistant RP achieved complete and sustained clinical and biochemical remission using the IL-1 receptor antagonist, Anakinra, for almost 30 months, despite the tapering started after 18 months of continuous therapy with Anakinra, associated to colchicine and a quick tapering and withdrawal of corticosteroids. Following the elective tapering of Anakinra, the patient remained stable for three months with a dose of an injection of 100mg of Anakinra three times per week, before suffering a severe pericardial relapse concurrent with the systemic onset of systemic BD. The clinical condition observed fulfilled the International Criteria for Behçet's Disease (ICBD), featuring recurrent oral and genital ulcerations, erythema nodosum and a positive pathergy test. The immediate reinitiation of Anakinra (100mg daily) led to the rapid and complete resolution of both the pericardial inflammation and all systemic mucocutaneous manifestations. Conclusions: This case highlights a potential pathogenetic overlap between refractory RP and serositis-dominant BD phenotypes, suggesting that isolated RP may, in select cases, represent an early mono-organ precursor of a systemic autoinflammatory propensity. Furthermore, it provides clinical rationale for considering IL-1 blockade in serositis-dominant BD, though larger prospective studies are needed to confirm these findings.