IgG4-related disease

IgG4-related disease (IgG4RD) is a rare chronic systemic inflammatory condition that forms masses (or growths) in various parts of the body. It can affect many different parts of the body at the same time, leading to swelling, inflammation and scarring of the affected organs. The disease is often associated with high levels of the IgG4 antibody, which is where its name comes from.

Common affected organs include:
• Tear glands (lacrimal glands) and salivary glands
• Thyroid gland
• Pancreas
• Bile duct system
• Aorta (the largest artery)
• Kidneys
• Lymph nodes
• Lungs

The disease tends to affect older males but can affect anyone. 

The exact cause of IgG4RD is unknown. It is an autoimmune disease where your own immune system becomes overactive and attacks other tissues in the body. It is postulated that the IgG4 antibodies do not directly cause the disease, but serve as a marker of active disease.

IgG4RD is rare and diagnosis can be challenging as it can appear similar to other conditions such as infections and cancers. A comprehensive assessment will usually involve: 

• Detailed history taking and physical examination
• Laboratory tests including blood counts, inflammatory markers such as Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), liver function test, kidney test and IgG4 levels (IgG subclasses). Urine tests may also be done.
• Imaging: CT, MRI or PET-CT scans may be performed to look at the extent of the affected organs and determine the best site for biopsy. 
• Tissue biopsy (taking a sample of tissue for examination under the microscope) is helpful to diagnose IgG4RD and exclude other similarly appearing conditions. Examples include biopsy of the salivary glands, tear-producing lacrimal glands, enlarged thyroid gland, pancreas / biliary system.

IgG4RD is a systemic condition that can be effectively treated with medications. The goal of treatment is to decrease disease activity while preventing organ damage. Treatment varies depending on the severity of disease, but often involves medications to suppress inflammation and calm down the immune system. 

• Corticosteroids are fast-acting medications that effectively suppress the immune system and are effective for treatment of IgG4RD. Steroids are usually given as oral tablets (prednisolone). In severe disease, higher doses may be given through a drip in the vein (intravenous infusion) initially before being switched to oral tablets. 
• Other immune suppression medications may be given in addition to steroids to reduce the need for long-term steroids and for control of disease activity.
o Rituximab is a type of biologic medication, a newer targeted medication that is used in treatment of IgG4RD. It may be given as part of treatment during disease flares (to induce remission) or as maintenance treatment to prevent flares.
o Other immune suppression medications such as methotrexate, azathioprine or mycophenolate mofetil may be used.

As multiple organ systems may be affected in IgG4RD, patients are often cared for by a multidisciplinary team of medical professionals, including a primary rheumatologist and other relevant subspecialty teams and allied health professionals. Your treatment plan will be carefully tailored to your symptoms, preferences, and goals of care. 

Additionally, to prevent infections when on high doses of immune suppression medications, prophylactic antibiotics and certain vaccinations are encouraged (e.g. influenza, pneumococcal, COVID-19, respiratory syncytial virus and shingles). Other co-existing medical conditions such as osteoporosis, high cholesterol, diabetes mellitus and high blood pressure will also be addressed as part of holistic care.

Patients with IgG4-related disease are able to live active lives with the right treatment and support. Some recommended lifestyle changes include:

• Eat a balanced diet. Avoid raw and partially cooked food to reduce risks of infections, especially if you are on medications that suppress the immune system (e.g. steroids).
• Avoid smoking.
• Stay active and exercise in moderation. Ensure sufficient rest and sleep well.
• Attend regular medical check-ups to monitor your health. Participate actively in your care and ask questions during your clinic consultations.
• Take your medications as prescribed, even when you feel well, to avoid disease flares.
• Seek medical attention early if you suspect that you have a disease flare.

Seek a doctor's advice. You will be referred to a specialist (rheumatologist) who can confirm the diagnosis and start you on the appropriate treatment. Once diagnosed, it is important to start treatment early and follow your rheumatologist’s advice. This condition is managed by the Division of Rheumatology and Allergy.