[Immunoglobulin-G4-related disease].

Area of Science:

• Immunology
• Pathology
• Rheumatology

Background:

• Immunoglobulin G4-related disease (IgG4-RD) was defined in 2001, unifying distinct clinical symptoms of fibroinflammatory conditions.
• Recent research has significantly advanced the understanding of IgG4-RD's pathophysiology over the past two decades.
• IgG4-RD presents with organ enlargement and fibrosis, often mimicking other conditions.

Purpose of the Study:

• To provide a comprehensive overview of IgG4-related disease.
• To elucidate the pathophysiological mechanisms underlying IgG4-RD.
• To discuss diagnostic challenges and therapeutic strategies, particularly differentiating from granulomatous diseases like ANCA-associated vasculitis (AAV).

Main Methods:

• Review of experimental and clinical studies on IgG4-RD.
• Analysis of the cellular infiltrate and cytokine milieu in IgG4-RD.
• Comparison of IgG4-RD with differential diagnoses, including granulomatous diseases and AAV.

Main Results:

• IgG4-RD involves a dense lymphoplasmacytic infiltrate (including IgG4+ plasma cells, T-helper cells, and M2 macrophages) that triggers chronic inflammation and fibrosis.
• Fibroblast activation leads to characteristic storiform fibrosis and obliterative phlebitis.
• Diagnostic challenges arise due to overlapping clinical and serological features with other conditions, such as elevated IgG4 levels or positive ANCAs in various diseases.

Conclusions:

• IgG4-RD is a complex fibroinflammatory disease with a well-defined pathophysiological basis.
• Accurate diagnosis requires careful differentiation from mimicking conditions, especially granulomatous diseases.
• Further research into pathophysiology opens new therapeutic avenues for IgG4-RD.