# Transudative pleural effusion in pleuritis associated with immunoglobulin G4‐related disease diagnosed by thoracoscopy under local anaesthesia

## TL;DR

A case of transudative pleural effusion caused by IgG4-related disease was diagnosed using thoracoscopy in an elderly man with multiple health issues.

## Contribution

This case highlights the rare occurrence of transudative effusion in IgG4-related disease and the diagnostic value of thoracoscopy.

## Key findings

- Thoracoscopy revealed lymphatic follicle hyperplasia and IgG4-positive plasmacytoid cells.
- Diuretics failed to resolve the effusion, necessitating further investigation.
- IgG4-related pleuritis was confirmed, emphasizing the need to consider inflammatory causes in unresponsive cases.

## Abstract

Immunoglobulin G4 (IgG4)‐related disease is a chronic inflammatory condition often characterized by exudative pleural effusions. However, transudative pleural effusions, like in the presented case of an 80‐year‐old man with multiple comorbidities, are less common but possible. Despite initial treatment with diuretics, the effusion persisted, prompting further investigation. Medical thoracoscopy revealed lymphatic follicle hyperplasia and an abundance of IgG4‐positive plasmacytoid cells, confirming IgG4‐related pleuritis. This case underscores the importance of considering inflammatory etiologies, such as IgG4‐related disease, when faced with unresponsive transudative pleural effusions. Thoracoscopy serves as a valuable diagnostic tool in such scenarios, allowing for precise diagnosis and appropriate management.

We report a unique case of transudative pleural effusion associated with IgG4‐related disease in an 80‐year‐old man with multiple comorbidities. Despite initial treatment with diuretics, the effusion persisted, prompting further investigation. Medical thoracoscopy revealed lymphatic follicle hyperplasia and an abundance of IgG4‐positive plasmacytoid cells, confirming IgG4‐related pleuritis.