Distinct Clinical Phenotypes and Treatment Responses in IgG4-Related Disease: Insights From a Tertiary Care Centre in Western India.

BACKGROUND

IgG4-related disease (IgG4-RD) is a rare fibroinflammatory disorder characterized by tumefactive lesions and IgG4+ plasma cell infiltration. While corticosteroids induce remission, high relapse rates necessitate steroid-sparing agents. Although well-studied in East Asia, comprehensive Indian data remain limited.

METHODS

This retrospective study (2018-2024) analyzed 60 biopsy-evaluated patients diagnosed per the 2020 Revised Comprehensive Diagnostic Criteria. All received glucocorticoid induction; steroid-sparing agents were initiated concurrently in 97%. Treatment response was assessed using the IgG4-RD Responder Index (complete response [CR]: RI < 3 with ≥ 2-point reduction; partial response [PR]: ≥ 2-point reduction with RI ≥ 3; relapse: ≥ 2-point rise after response).

RESULTS

The cohort (n = 60) was 57% male, mean age of 46.4 ± 16.1 years. Most had definite IgG4-RD (63%), and 42% presented with multisystem involvement. Distinct from East Asian cohorts, retroperitoneal fibrosis (32%) and lung involvement (28%) predominated, with pancreatic (5% vs. 60% in Japan) and salivary gland disease (25% vs. 72%) were rare. Histopathology revealed universal lymphoplasmacytic infiltrates (100%) and fibrosis (93%), but infrequent storiform fibrosis (7%) and obliterative phlebitis (12%). Treatment yielded a 90% response rate at 6 months (28% CR, 62% PR), improving to 52% CR at 2 years. Despite excellent induction, cumulative relapse reached 66% at a median of 13 months follow-up, underscoring the disease's chronic nature. In a small subgroup receiving rituximab plus methotrexate (n = 4), 75% achieved CR with no documented relapses at 2 years; larger studies are needed to confirm this signal. One death occurred from urosepsis.

CONCLUSION

Indian IgG4-RD patients exhibit younger onset, retroperitoneal-lung predominance, and minimal pancreatic involvement. Early combination immunosuppression provides excellent initial responses but cannot prevent the disease's relapsing nature, underscoring the need for long-term maintenance strategies and region-specific management approaches.