IgG4-related sclerosing cholangitis: navigating diagnostic dilemmas and the challenge of relapse.

BACKGROUND

Immunoglobulin G4-related sclerosing cholangitis (IgG4-SC), also termed IgG4-related cholangitis (IRC), is a challenging immune-mediated biliary disease, frequently mimicking malignancies such as cholangiocarcinoma (CCA) or other sclerosing cholangitides like primary sclerosing cholangitis (PSC). Accurate diagnosis is critical to avoid unnecessary surgical interventions.

OBJECTIVE

This mini-review aims to synthesize the most current evidence on the pathogenesis, diagnostic pitfalls, and management strategies for IgG4-SC, with a focused discussion on overcoming diagnostic dilemmas and addressing the significant challenge of disease relapse.

KEY FINDINGS: The pathogenesis of IgG4-SC involves a complex interplay of genetic predisposition, environmental triggers (e.g., industrial vapors, dust, gases, fumes, and asbestos), and dysregulated adaptive immunity. A distinctive CD4+ T-cell response, dominated by T-helper 2 (Th2), follicular helper T (Tfh) cells, and regulatory T cells (Tregs), drives B-cell activation, oligoclonal expansion of IgG4+ plasmablasts, and progressive fibrosis. Notably, the discovery of IgG4/IgG1 autoantibodies against annexin A11 and laminin 511-E8 has provided insight into potential direct pathogenic mechanisms. Diagnosis relies on a multimodal approach integrating clinical presentation, characteristic imaging findings, elevated serum IgG4 levels (with levels >2× ULN being suggestive, and >4× ULN being highly specific), the IgG4/IgG1 ratio (>0.24), other organ involvement (notably type 1 autoimmune pancreatitis, AIP), supportive histopathology, and a rapid response to corticosteroid therapy. Despite high initial response rates to steroids, relapse occurs in 30%-50% of patients. Maintenance therapy with steroid-sparing immunomodulators (e.g., azathioprine, mycophenolate mofetil) or B-cell depleting agents such as rituximab is often required. The anti-CD19 monoclonal antibody inebilizumab has emerged as a potent new option for maintaining remission.

CONCLUSION

Maintaining a high index of clinical suspicion for IgG4-SC is essential in patients with obstructive jaundice and biliary strictures. Future efforts should focus on validating specific biomarkers (e.g., circulating plasmablasts, autoantibody profiles) and developing evidence-based protocols for long-term management to prevent fibrotic complications and reduce the relapse rate.