Background/Purpose: IgG4-related disease (IgG4-RD) is a systemic fibro-inflammatory disorder that can affect almost any organ system. Response to corticosteroids(CS) is typically prompt although adverse effects are commonplace and relapses frequently occur during withdrawal. There is evidence to suggest that rituximab (RTX) may be an effective alternative however as yet, the optimal RTX treatment regimen for IgG4RDremains unclear. In this retrospective study, we report the use of a RTX treatment protocol for multi-system IgG4RD in a large single tertiary center cohort.

Methods: Patients were selected from an IgG4RD multi-disciplinary service receiving referrals from the catchment of North West London. Patients diagnosed with IgG4-RD received RTX according to local protocol guided by B cell repopulation (to a level of > 10 cells/uL) for a target period of two years. The electronic patient records were reviewed to record presentation and outcome data over the course of their RTX therapy.

Results: In total, 45 patients received treatment with RTX. 1 patient was excluded from analysis due to insufficient follow up data. The median age was 62 and 66% were male. Multiple ethnic backgrounds were represented; 20% black, 20% white and 60% Asian. The average number of organs affected was 2.9 (range 1-7) and the average IgG4-RD Responder Index (RI) prior to treatment was 10.02. 8/44 (18%) were on another conventional immunosuppressant at the time of RTX induction and 27/44 (61%) had concurrent treatment with CS. The proportions of the 27 patients remaining on CS at 9, 12 and 24 months were 66%, 54% and 19% (average dose at 2 years 3.8mg). All patients demonstrated reduced disease activity post RTX with an average IgG4-RI of 2.4 at most recent review (76% reduction). 34 patients had follow-up imaging and all had a degree (100%) of disease response; 2/34 (6%) stable; 21/34 (62%) partial response; 11/34 (33%) had a complete response. Intercurrent flares did occur in 9 patients, 7 of whom had concurrent B cell repopulation (78%). All 7/7 (100%) patients treated with further RTX responded positively. 15 patients completed two years of consistent RTX-induced B cell depletion with no subsequent flares (average follow up 15 months, median 10 months, range 1-51 months). The only 2 patients requiring >2 years maintenance RTX therapy had isolated pituitary disease. 12/45 (27%) of the entire cohort experienced an adverse event including infection requiring admission (4), hypogammaglobinaemia (2), infusion reaction (1) and death (5; 11%; average age 81).

Conclusion: In this cohort of patients treated with RTX for IgG4-RD, all patients demonstrated improved disease activity according to IgG4-RD RI and available imaging. Flares did occur but most often in the presence of measurable B cell repletion and all patients re-treated with further RTX responded. In those who discontinued treatment after >2 years of B cell depletion therapy, there were no further flares over an average follow-up duration of almost 15 months. This retrospective study indicates that protocolled management of IgG4RD with RTX is an effective treatment option for IgG4-RD. Patient selection is important to minimize the risk of complications.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/single-center-experience-of-rituximab-treatment-for-igg4-rd-disease-in-a-large-multi-ethnic-cohort/