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IgG4-related Disease: Causes, Symptoms & Treatment

IgG4-related disease is a rare immune-mediated condition causing inflammation and fibrosis across multiple organs. Early diagnosis and treatment are essential to prevent permanent organ damage.

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Things worth knowing about "IgG4-related disease"

IgG4-related disease is a rare immune-mediated condition causing inflammation and fibrosis across multiple organs. Early diagnosis and treatment are essential to prevent permanent organ damage.

What is IgG4-related disease?

IgG4-related disease (IgG4-RD) is a rare, chronic inflammatory systemic condition characterized by the accumulation of IgG4-positive plasma cells in affected tissues, accompanied by progressive scarring known as fibrosis. Almost any organ can be involved, but the most commonly affected include the pancreas, salivary glands, bile ducts, kidneys, lungs, and eye sockets (orbits).

The condition was only recognized as a distinct disease entity in the early 2000s and is therefore still frequently misdiagnosed or detected late in clinical practice.

Causes and Pathogenesis

The exact causes of IgG4-RD remain incompletely understood. It is considered an immune-mediated disease in which the immune system malfunctions and attacks the body's own tissues. The following mechanisms have been proposed:

Immune dysregulation: Certain T-helper cell subtypes (Th2 cells and regulatory T cells) promote IgG4 antibody production and the release of pro-fibrotic cytokines.
Genetic predisposition: Certain genetic profiles may increase susceptibility, although no clear hereditary pattern has been established.
Allergic and environmental factors: An association with atopic conditions such as asthma and allergies has been observed, though a causal relationship has not been proven.

Symptoms

The clinical presentation of IgG4-RD depends largely on which organ or organs are involved. Common signs and symptoms include:

Swelling of glands, salivary glands, or lymph nodes
Jaundice (icterus) due to involvement of the bile ducts or pancreas
Abdominal pain in cases of autoimmune pancreatitis
Visual disturbances or periorbital swelling with orbital involvement
Renal impairment due to kidney involvement
Cough or shortness of breath with pulmonary involvement
General symptoms such as fatigue and unintentional weight loss

Notably, many patients do not experience pronounced systemic symptoms even when multiple organs are simultaneously affected.

Diagnosis

Diagnosing IgG4-RD is challenging because no single definitive diagnostic test exists. The diagnosis is based on a combination of:

Blood tests: Elevated serum IgG4 levels are an important indicator, but are not elevated in all patients and are not specific to this disease alone.
Imaging: Computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound can reveal characteristic changes in affected organs.
Tissue biopsy: Considered the gold standard. Histological findings include a dense infiltration of IgG4-positive plasma cells, storiform (whorling) fibrosis, and obliterative phlebitis (closure of small veins).
Clinical response: A rapid and marked response to corticosteroid therapy supports the diagnosis.

Treatment

The standard first-line treatment for IgG4-RD is corticosteroid therapy (e.g., prednisolone), which leads to rapid improvement in most patients. The following treatment options are available:

Corticosteroids: First-line therapy for active disease. The dose is gradually tapered over several months.
Immunosuppressants: Agents such as azathioprine, mycophenolate mofetil, or methotrexate are used in relapsing disease or as steroid-sparing agents.
Rituximab: A monoclonal antibody targeting the B-cell marker CD20, used in severe or relapsing cases with favorable outcomes.
Surgical intervention: In specific situations, such as bile duct obstruction, surgical procedures may be required.

Without treatment, progressive fibrosis can lead to permanent organ damage. Regular follow-up examinations are therefore essential to detect relapses early.

References

Kamisawa T, Zen Y, Pillai S, Stone JH. IgG4-related disease. Lancet. 2015;385(9976):1460-1471.
Stone JH, Zen Y, Deshpande V. IgG4-related disease. New England Journal of Medicine. 2012;366(6):539-551.
Bhatt DL et al. (Eds.). Harrison's Principles of Internal Medicine, 21st Edition. McGraw-Hill Education, 2022.

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