Clinical and laboratory characteristics of IgG4-related disease involving multiple organs.

Introduction: IgG4-RD is a rare but increasingly recognized systemic condition characterized by complex clinical manifestations and multi-organ involvement, often leading to misdiagnosis or delayed diagnosis. This study aims to elucidate the clinical features of IgG4-RD and evaluate the diagnostic and therapeutic utility of key laboratory indicators.

Method: We conducted a retrospective analysis of IgG4-RD patients, comparing laboratory profiles across different organ involvement patterns. The diagnostic and therapeutic value of serum IgG4 levels in IgG4-RD was evaluated, with comparative analyses of serum IgG4 levels extended to non-IgG4-RD patients.

Results: Distinct patterns of laboratory markers were observed across affected organs, with elevated IgG and ESR levels consistently noted. The optimal diagnostic cutoff for serum IgG4 in IgG4-RD was 1.94 g/L, while a cutoff of 9.05 g/L effectively identified multi-organ involvement. Following 6 months of standardized treatment, serum IgG4 levels in IgG4-RD patients decreased significantly. Notably, ANCA-associated vasculitis patients exhibited markedly elevated serum IgG4 levels, which remained unchanged post-treatment.

Conclusions: The integration of serum IgG4 with other laboratory markers enhances diagnostic precision for IgG4-RD. Elevated serum IgG4 levels are associated with multi-organ involvement, underscoring their utility in assessing disease extent. Serum IgG4 is indispensable for monitoring therapeutic response. Given the overlapping clinical features between ANCA-associated vasculitis and IgG4-RD, accurate differentiation is essential for optimal clinical management. Key Points • IgG4-RD predominantly affects middle-aged and elderly males, yet its occurrence in younger individuals and less commonly involved organs (e.g., brain and heart) warrants attention. • Affected organs demonstrate distinct laboratory marker profiles, providing valuable insights for clinical diagnosis and therapeutic strategies. • Serum IgG4 levels are instrumental in diagnosing, assessing disease progression, and monitoring treatment response, though their interpretation should be integrated with other clinical indicators. • In ANCA-associated vasculitis, serum IgG4 levels are markedly elevated but remain stable post-treatment, offering a potential diagnostic criterion to differentiate it from IgG4-RD.