Makindo Medical Notes

Immunoglobulin G4-related disease (IgG4-RD) is a systemic condition characterized by fibroinflammatory infiltration of various organs by plasma cells that express IgG4 (immunoglobulin G subclass 4).

About IgG4-Related Disease

• IgG4-related disease (IgG4-RD) is a systemic fibroinflammatory disorder caused by an immune response involving IgG4-positive plasma cells.
• First recognized in 2001 in association with autoimmune sclerosing pancreatitis.

Aetiology

• IgG4-RD involves the infiltration of multiple organs by inflammatory IgG4-positive plasma cells.
• If left untreated, it can lead to fibrosis and permanent organ damage. The disease can affect nearly any organ or structure in the body.

Clinical Features

• Coronary artery stenosis, causing chest pain.
• Pericardial thickening, presenting as chest pain.
• Chronic subdural disease (accumulation of fluid in the subdural space).
• History of autoimmune diseases.
• Abdominal pain, often related to pancreatitis.
• Salivary gland enlargement, often with associated lymphadenopathy.
• Skin manifestations, such as rashes or nodules.

Investigations

• Fluorodeoxyglucose (FDG) PET scans: May show increased uptake in affected organs, indicating inflammation.
• Biopsy: Immunohistochemistry should show IgG4-positive plasma cells, which should account for more than 40% of the total IgG-positive plasma cells. A serum IgG4 level higher than 135 mg/dL supports the diagnosis.

Management

• Steroids: Corticosteroids are the first-line treatment, with disease remission seen in about 90% of cases.
• Immunosuppressive drugs: For refractory cases, disease-modifying antirheumatic drugs (DMARDs) like azathioprine, methotrexate, or mycophenolate mofetil may be considered, although there is limited supporting evidence.
• Monitoring: Regular monitoring of serum IgG4 levels and imaging is crucial to ensure disease control after the initiation of therapy and during the maintenance phase.

References

• Immunoglobulin G4-related Disease