Diagnostic pitfalls in systemic juvenile idiopathic arthritis: insights from 6 misdiagnosed cases

Objective Systemic juvenile idiopathic arthritis (sJIA) is a diagnosis of exclusion with nonspecific early manifestations. Misdiagnosis is common due to overlap with infections, autoinflammatory diseases, and malignancies. We aimed to characterize a series of patients initially diagnosed with sJIA who subsequently reclassified following further evaluation were. Methods We retrospectively reviewed the clinical records, laboratory findings, genetic analyses, and imaging data of six pediatric patients initially diagnosed with sJIA but later revised to alternative diagnosis after further investigations. These patients were enrolled at Shenzhen Children's Hospital between January 2011 and December 2022. Results All six patients initially fulfilled at least one set of sJIA classification criteria. All patients presented with recurrent fever (100%, 6/6), three had arthritis (50%, 3/6), and five exhibited rash (83.3%, 5/6). Elevated inflammatory markers were observed in all patients (100%, 6/6). The median age at initial sJIA diagnosis was 64 months (IQR, 24–145). The median delay from initial diagnosis to final diagnosis was 9.5 months (IQR, 5–12). Three patients (50%, 3/6) were considered to have refractory sJIA prior to diagnostic revision. Final diagnoses included autoinflammatory diseases ( n = 3), Takayasu arteritis ( n = 1), inflammatory myofibroblastic tumor ( n = 1), and suspected congenital hemophagocytic lymphohistiocytosis ( n = 1). Conclusions sJIA is defined by classification criteria and represents a diagnosis of exclusion, requiring long-term dynamic reassessment to distinguish it from other diseases with overlapping clinical features. Early recognition of atypical manifestations and timely comprehensive evaluation are essential to avoid misdiagnosis, particularly in distinguishing monogenic autoinflammatory disorders and malignancies.