# IgG4-Related Disease (IgG4-RD) with Unique Combined Generalized Skin Rashes and Biliary Tract Manifestation: A Comprehensive Immunological Analysis

## TL;DR

This paper reports a rare case of IgG4-related disease with combined skin and biliary tract symptoms, analyzing immune cell changes to better understand the condition.

## Contribution

The first comprehensive immunological analysis of IgG4-RD with combined skin and biliary tract manifestations.

## Key findings

- Elevated serum IgG4 and increased IgG4-positive plasma cells in biopsies confirmed IgG4-RD.
- Altered T and B cell subsets suggest a role for regulatory lymphocytes in disease pathogenesis.
- Combined skin and biliary tract involvement in IgG4-RD is a previously unreported clinical presentation.

## Abstract

IgG4-RD is a multisystem fibroinflammatory disease characterized by the infiltration of tissues by IgG4 plasma cells. Combined skin and biliary tract involvement in IgG4-RD has not been described. We present perhaps the most comprehensive analysis of lymphocyte subsets in the first case of IgG4-related generalized skin rash and first case of combined skin and biliary tract manifestations. A 55-year-old male presented with painful jaundice and generalized macular pigmented pruritic eruptions, and CT abdomen revealed biliary obstruction. Ampulla and skin biopsies were subjected to histology and immunostaining. Naïve, central memory (TCM), effector memory (TEM), terminally differentiated effector memory (TEMRA) subsets of CD4+ and CD8+ T cells, T follicular helper subsets, naïve, transitional, marginal zone (MZ), germinal center (GC), IgM memory, and class-switched memory (CSM) B cells, and T follicular regulatory, regulatory B cells, CD4 Treg, and CD8 Treg were analyzed. Serum IgG4 was elevated at 448 mg/dL. Ampula biopsy showed lamina propria fibrosis and increased IgG4-positive plasma cells. Skin punch biopsy showed lymphoplasmacytic infiltrates with a 67% ratio of IgG4+:IgG+ plasma cells. CD4+TN and CD4+TCM decreased, whereas CD4+TEM increased. Naïve B cells increased; transitional, MZ, CSM, GC B cells, and plasmablasts decreased compared to control. CD4 Treg increased, whereas CD8 Treg and Breg decreased. In conclusion, IgG-RD may present with combined biliary tract and generalized dermatological manifestations. Changes in regulatory lymphocytes suggest their role in the pathogenesis of IgG4-RD.