Case report of systemic inflammatory response syndrome in refractory gout mimicking infective endocarditis: Diagnosis via PET–CT and successful treatment with firsekibart

Background Severe gout can manifest as systemic inflammatory response syndrome (SIRS), closely mimicking infective endocarditis (IE) and presenting a diagnostic challenge, particularly in patients with complex comorbidities. Objectives This study aimed to describe the diagnostic pivot via positron emission tomography/computed tomography (PET–CT) and successful therapeutic management using a novel IL-1β inhibitor in a patient with refractory gout SIRS misdiagnosed as IE. Methods A 59-year-old male with recent percutaneous coronary intervention, chronic kidney disease, and gastrointestinal bleeding presented with recurrent high-grade fever and shock. Initial suspicion of IE was based on echocardiographic mitral valve “vegetation,” but symptoms persisted despite prolonged broad-spectrum antibiotic regimens. Whole-body PET–CT was utilized to investigate the occult inflammatory focus. Results PET-CT ultimately ruled out cardiac infection, revealing intense hypermetabolic activity in multiple joints consistent with systemic gout inflammation. Given that traditional anti-inflammatory therapies were contraindicated, treatment with the novel anti-IL-1β monoclonal antibody firsekibart was initiated. The patient achieved rapid clinical remission without observed adverse events or tuberculosis reactivation during the 6-month follow-up. Conclusions This case underscores the critical role of PET–CT in differentiating severe gout from IE in complex clinical presentations. The findings suggest the potential utility of targeted IL-1β inhibition with firsekibart as a therapeutic strategy for patients with multiple comorbidities where conventional anti-inflammatory agents are unsuitable.