Table 2 Biomarkers of IgG4-related disease
From: IgG4-related disease—rare but you should not forget it
Type of biomarker | Examples | Comments |
|---|---|---|
Diagnosis | Serum IgG4 | Elevated in 55–97% of patients. Correlates with disease burden |
Serum IgG4/IgG ratio | When > 10%, it increases specificity in the case of normal serum IgG4 | |
Serum IgE and eosinophils | Elevated in 30% of patients regardless of atopic background | |
CSF IgG4 indices | High in IgG4-related hypertrophic pachymeningitis | |
Plasmablasts and plasma cells | Expanded in peripheral blood regardless of serum IgG4 concentration | |
Serum C3 and C4 | Reduced levels suggest active disease, particularly in patients with IgG4-related kidney disease (mostly tubulointerstitial nephritis) | |
CD4 and/or CD8 SLAMF7 + CTLs | Expanded in peripheral blood during active disease | |
18FDG-PET | Useful for staging purposes and the definition of alternative biopsy sites. Caution when interpreting lymph nodes (indistinguishable from reactive and neoplastic lymph nodes) | |
Disease activity | Serum IgG4, IgE, and eosinophils | Decrease with disease response to treatment. It may not normalize at disease remission. Marked (> 2x) increase after remission should raise the possibility of disease flare |
Serum IgG4/IgG ratio | Decrease in disease response to treatment | |
CSF IgG4 indices | Decrease in disease response to treatment | |
Plasmablasts and plasma cells | Decrease in disease response to treatment and increase at flare | |
Serum C3 and C4 | They may normalize in remission and decrease during flares, especially in kidney involvement | |
Serum ESR/CRP* | Correlate with disease activity, especially in retroperitoneal and aortic involvement | |
CD4 and/or CD8 SLAMF7 + CTLs | Decrease with disease response to treatment and increase with flare | |
18FDG-PET | 18FDG uptake reduced after treatment. Caution when interpreting lymph nodes (indistinguishable from reactive and neoplastic lymph nodes) |