IgG4-Related disease: From diagnosis to remission.

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disorder that can affect many organ systems. This chapter provides a comprehensive overview of current knowledge regarding IgG4-RD, addressing key questions about disease mechanisms, diagnostic approaches, and therapeutic strategies. We examine the diverse clinical manifestations ranging from glandular enlargement to life-threatening vascular involvement, emphasizing the importance of recognizing both inflammatory and fibrotic disease phenotypes. Diagnostic approaches integrate clinical symptoms, imaging findings, histopathological features, and serological markers while excluding mimicking conditions. Treatment strategies have evolved significantly with the introduction of B cell depletion therapy, particularly inebilizumab. Current treatment paradigms must prioritize glucocorticoid-sparing approaches, though maintenance therapy considerations remain complex. Critical knowledge gaps persist regarding optimal biomarkers for disease activity, standardized remission criteria, and the precise etiopathogenesis of IgG4-RD. Despite therapeutic advances, challenges remain in balancing effective disease control with minimizing the harms of long-term immunosuppression, emphasizing the need for continued research into targeted therapies.