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Case Reports
. 2025 Sep;44(9):3765-3769.
doi: 10.1007/s10067-025-07584-9. Epub 2025 Jul 24.

IgG4-related arthritis revealed by synovial biopsy: a case-based review

Alessandra Rai  1   2 , Giorgia Citriniti  3 , Marianna Oliva  3 , Giuseppe Germanò  3 , Riccardo Valli  4 , Alberto Cavazza  4 , Carlo Salvarani  5   3 , Niccolò Possemato  3
Affiliations
Case Reports

IgG4-related arthritis revealed by synovial biopsy: a case-based review

Alessandra Rai et al. Clin Rheumatol. 2025 Sep.

Erratum in

Abstract

Introduction: IgG4-related disease (IgG4-RD) is a systemic autoimmune condition characterized by fibroinflammatory lesions, potentially occurring at any anatomical site. Typical histopathological features include dense lymphoplasmacytic infiltrates rich in IgG4 + plasma cells, storiform-pattern fibrosis, and obliterative phlebitis. Diagnosing IgG4-RD remains challenging due to its heterogeneous features. Here, we report a rare case of IgG4-RD diagnosed by a synovial biopsy of the wrist.

Case report: An 80-year-old man presented with relapsing right wrist arthritis. Laboratory tests showed elevated erythrocyte sedimentation rate and C-reactive protein, while immunological profiles remained negative. Imaging showed severe erosive arthritis of the carpal bones. A synovial biopsy revealed low-grade synovitis (grade 2 according to Krenn score), with histological examination showing significant infiltration of IgG4 + plasma cells (up to 40 per high-power field, with an IgG4/IgG ratio of 40%). 18-Fluorodeoxyglucose-positron emission tomography (PET) showed increased uptake in lymph nodes, with excisional biopsy revealing reactive changes along with a focal increase in IgG4-positive plasma cells (up to 70 per high-power field) and an IgG4/IgG ratio of 50%. Consequently, IgG4-RD was diagnosed, and corticosteroid therapy was initiated, resulting in clinical improvement and reduced IgG4 levels.

Discussion: This case illustrates a rare case of IgG4-RD involving joints and lymph nodes, diagnosed by synovial biopsy. The presence of IgG4-positive plasma cells in the joint and lymph nodes strongly supported the diagnosis of IgG4-RD. Synovial biopsy can play a significant role in the diagnostic work-up of arthritis, particularly in cases that are difficult to categorize. Further studies are needed to better characterize IgG4-related arthritis.

Keywords: Arthritis; IgG4-related disease; Synovial Biopsy.

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Conflict of interest statement

Declarations. Consent for publication: This work has not been published previously nor is it currently under consideration for publication elsewhere. Consent to participate: Written informed consent was obtained from the patient included in the study. The patient has consented to the publication of the case report and accompanying images. Disclosure: None.

References

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