# Perineural Spread of Orbital Immunoglobulin G4-Related Disease: A Case Report

## TL;DR

This case report describes a rare instance of orbital IgG4-related disease spreading to nerves, highlighting the challenges in diagnosis and treatment.

## Contribution

The paper presents a rare case of perineural spread of orbital IgG4-related disease and successful treatment with azathioprine.

## Key findings

- The patient showed elevated IgG4 levels and imaging confirmed involvement of orbital structures and trigeminal nerves.
- Azathioprine normalized IgG4 levels and resolved symptoms after prednisone and rituximab failed.
- This case emphasizes the need for increased awareness of IgG4-RD's diverse manifestations for timely diagnosis.

## Abstract

Immunoglobulin G4-related disease (IgG4-RD) is a rare, immune-mediated fibroinflammatory condition that can affect multiple organs. It is characterized by elevated serum IgG4 levels, lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis. Diagnosis can be challenging due to limited awareness amongst clinicians and its wide range of clinical manifestations. We present a case of an elderly woman with bilateral orbital IgG4-RD and perineural spread, a rare manifestation of the disease. Serological testing showed markedly elevated IgG4 levels, and imaging revealed bilateral extraocular muscle enlargement and inflammatory involvement of the lacrimal glands, orbital fat, and trigeminal nerves. The patient initially responded to oral prednisone but discontinued therapy due to side effects. Rituximab, a second-line treatment, caused anaphylaxis, prompting a switch to azathioprine, which led to normalization of IgG4 levels and resolution of symptoms. This patient's positive response to azathioprine highlights the importance of individualized therapeutic strategies in managing this complex condition. This case also underscores the importance of recognizing IgG4-RD as a potential cause of orbital and neurological symptoms. Increased awareness of its diverse clinical and imaging features can facilitate early diagnosis and treatment. To date, this is one of the few documented cases of orbital IgG4-RD with perineural spread, emphasizing the need for further research and reporting to enhance understanding of this rare manifestation.