❓What❓
- Insidious, progressive, infiltrative disease marked by fibroinflammatory, tumor-like lesions that stain ⊕ for IgG4, show “storiform fibrosis,” & eosinophilic/atopic features (↑ Th2 → ↑ IL-5)
❓Epidemiology❓
- Middle age, M > F
❓Presentation❓
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❓Diagnosis❓
Path to the Problem ⛰️
- IgG4-RD is the great mimicker of our generation: if you see a syndrome of eosinophilia/atopy ⊕ ___ , IgG4-RD has to join the DDx (—Dr. Mark Heslin)
Diagnosis (2020 Dx Criteria) 🧠
- Compatible syndrome ⊕ consistent pathology ⊕ IgG4 > 135mg/dL = definitive
- Compatible syndrome ⊕ consistent pathology = probable
- Compatible syndrome ⊕ IgG4 > 135mg/dL = possible
- If no extra-vascular tissue sites are available for sampling, empiric immunosuppression with a therapeutic response may provide an answer:
Lab findings 🟠
- ↑ IgG4 > 135 mg/dL (75-90% sensitivity; > 500 mg/dL ~90% specific)
- ↑ IgE (often > 1000 mg/dL, 60% sensitivity)
- Eosinophilia (~30% sensitivity)
- Polyclonal hypergammaglobulinemia (normal CRP)
Pathology 🔬
- Lymphoplasmocytic infiltrates enriched in IgG4+ plasma cells (100%)
- Storiform fibrosis (74%)
- Obliterative phlebitis (40%)
- Eosinophilic infiltration (40%)
🔬 Note: IgG4+ plasma cells are very non-specific (even in large quantities), so the ratio of IgG4+/IgG+ plasma cells should be >40% regardless of the infiltrated organ examined
🔬 Note: granulomas, giant cells, neutrophilic infiltrates are unusual
📚 References 📚
