Navigating the Spectrum: Atypical Pulmonary Involvement in Immunoglobulin G4-Related Disease

Abstract

Immunoglobulin G4-related disease (IgG4-RD) is a systemic condition known to affect multiple organ systems. While its manifestations are diverse, pulmonary involvement, especially of the pleura, remains less common. We report the case of a 99-year-old Saudi male with a medical history of diabetes mellitus, chronic kidney disease, and hypertension. He presented with dyspnea and syncope, with radiological findings revealing pleural effusion and a mass in the right hemidiaphragm. Laboratory investigations highlighted elevated serum IgG4 levels, and histopathological evaluation confirmed the diagnosis of IgG4-RD. Notably, the patient's thoracic histopathology differed from typical IgG4-RD presentations, emphasizing the variability of the disease. This case underscores the significance of recognizing IgG4-RD as a potential cause of unexplained pleural effusion. It also highlights the need for a comprehensive diagnostic approach, integrating laboratory values, histopathological findings, and clinical context. Given the potential variability in thoracic IgG4-RD histopathology, clinicians should maintain a heightened awareness of this condition to avoid missed diagnoses.

Keywords: igg4 -related disease; igg4 disease; igg4 pleural involvement; immune disorder; immunoglobulin g-4 (igg4) related systemic disease.

Figure 1. Chest X-ray from October 2020 showing right lower lobe consolidation or atelectasis and a small right-sided pleural effusion (white arrow). The left costophrenic angle appears clear, with no evident signs of pneumothorax.

Figure 2. Chest X-ray from July 2021 illustrating the progression of the disease. The image reveals a small right-sided pleural effusion (white arrow) with adjacent collapse or consolidation. The left lung remains clear, and no signs of pneumothorax are visible.

Figure 3. CT shows pericardial/pleural effusions, right lower lobe collapse (white arrows), and abnormal density at the right hemidiaphragm (yellow arrows).

Figure 4. Immunohistochemical staining revealed IgG4-positive plasma cells.