What is IgG4-Related Disease?
IgG4-related disease (IgG4-RD), also known by several other names, is a condition that can affect multiple parts of the body and involves inflammation and abnormal growths, the cause of which is unknown. Any organ can be affected by this disease, but it’s commonly found in the pancreas, kidneys, certain structures around the eyes, salivary glands, and area behind the abdominal cavity.
The key feature of this disease is the presence of a high number of specific immune cells (IgG4 positive plasma cells) mixed with other immune cells and scar tissue, causing blood vessel obstruction and attracting a certain type of white blood cell (eosinophils). This condition often elevates the levels of a specific type of protein (IgG4) in the blood. The disease pattern looks similar across different organs which makes it resemble another disease called systemic sarcoidosis.
Because the abnormal growths caused by IgG4-RD can look similar to tumors, infections, or immune system diseases, it’s often misdiagnosed as cancer. Even though it’s frequently not recognized due to the lack of a comprehensive approach in assessing it, patients generally recover well after receiving a specific type of medication called glucocorticosteroids. In fact, the effectiveness of these steroids in treating IgG4-RD is so powerful that it could be used to help diagnose the disease.
What Causes IgG4-Related Disease?
The exact cause of this condition isn’t completely understood, but it’s believed to have links to several factors. These include a person’s genetic makeup, bacterial infections that can cause the body to mistakenly attack its own cells (a process called molecular mimicry), and autoimmune diseases, where the immune system mistakenly attacks the body’s own tissues and organs.
Risk Factors and Frequency for IgG4-Related Disease
The exact number of people affected by IgG4-related disease (IgG4-RD) is not certain.
What else can IgG4-Related Disease be?
The conditions similar to IgG4 related disease that doctors might need to rule out include:
- Autoimmune pancreatitis
- Eosinophilia
- Hypereosinophilic syndromes
- Lymphadenopathy
- Multicentric Castleman disease
- Orbital disease
- Plasma cell neoplasm
- Polyclonal hypergammaglobulinemia
- Salivary and lacrimal gland enlargement