Background/Purpose: IgG4 related disease (IgG4-RD) is a rare immune-mediated condition, increasingly being recognised as a multi-organ disorder. It is a relatively new entity and the precise prevalence is not known. It is a chronic fibro-inflammatory condition with raised levels of immunoglobulin G4 and accumulation of plasma cells and fibrosis in the affected tissue. A recent 3-step classification criteria has been developed jointly by ACR/EULAR to help to diagnose IgG4-RD. It includes a variety of exclusion criteria as well as weighted inclusion criteria.

Methods: We present a retrospective observational study of patients seen at Guy’s and St Thomas’ NHS Foundation Trust Hospitals, London, UK. The data conducted was analysed for clinical presentation, laboratory markers of inflammation, immunoglobulin subsets, autoantibody profiles, imaging and histopathology and compared to the 2019 ACR/EULAR criteria to determine confirmed diagnosis of IgG4-RD. Data was also collected post standard-of-care treatment, including patient clinical outcomes and possible improvement. IgG4 Responder Index was also calculated for each patient before and after treatment.

Results: The study included a multi-ethnic cohort of 83 patients with multi-organ involvement.

Fifty-nine out of eighty-three analysed were classed as confirmed IgG4-RD rather than possible (71%). Seventy-one patients had biopsies of which 49 (91% of confirmed IgG4-RD) were consistent with IgG4-RD. Fifty patients had PET-CT scanning of which uptake was seen in 76% of those with confirmed IgG4-RD (26/34). Immunoglobulin IgG subclass analysis showed significantly higher IgG4 levels in the confirmed IgG4-RD group. Treatments were with corticosteroids and immunosuppressants such as azathioprine, methotrexate, mycophenolate, cyclophosphamide and rituximab.

Post treatment, IgG4-RI was significantly improved. Post-treatment IgG4 levels, as well as inflammatory markers, were significantly reduced in the patients with IgG4-RD disease who had had an initially high IgG4 level (31/43). This was correlated with clinical improvement in twenty-four (77%) of those patients. Fifty-three patients in total showed clinical improvement after treatment (79%). Of the biologics patients (n=15), eleven showed improvement (73%).

Conclusion: IgG4-RD is a fibro-inflammatory disorder involving multiple organs. If not treated adequately patients may develop severe organ damage. It often responds to corticosteroids but may require other immunosuppressive therapy as we have shown, with IgG4 levels and IgG4-RI providing good markers of disease activity. Treatment with biologics such as B cell depletion therapy results are encouraging. It will be interesting to see the outcomes of future biologics controlled trials in IgG4-RD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/igg4-related-disease-response-to-immunosuppressive-therapy-a-single-centre-retrospective-study-in-the-united-kingdom/