# Treatment options for IgG4-related disease
IgG4-related disease is an inflammatory condition in which the body produces too much of a specific type of antibody (IgG4), leading to thickening and scarring in various organs. Treatment varies greatly from case to case and depends on which organs are involved, how active the disease is, and how well someone has responded to previous therapies.
Observation and watchful waiting
Not every diagnosis of IgG4-related disease immediately leads to medication use. Patients without symptoms or with very mild manifestations are often observed first without direct therapeutic intervention.
Recent research into the outcomes of watchful waiting shows that some patients can remain without treatment for years, while others show progression. The doctor determines together with the patient which approach best fits the severity and extent of the disease. This approach prevents unnecessary medication use in people with minimal active inflammation.
Corticosteroids
ProveniIncluded in official guidelines, or approved by EMA or FDA
Corticosteroids (active ingredient in medications such as prednisone or methylprednisolone) have long been the standard treatment and remain the first step for many patients. The steroids suppress the overactive inflammatory response of the immune system, causing swelling and inflammation to decrease.
Treatment is usually built up step by step: one starts with a higher dose to get the inflammation under control, then gradually tapers down as the situation improves. This gradual reduction helps the body adjust and reduces side effects.
**Known side effects** of long-term corticosteroid use include weight gain, insomnia, mood swings, elevated blood sugar, thinning bones (osteoporosis), and increased infection risk. These side effects are greater the higher and longer the dose.
Rituximab
ProveniIncluded in official guidelines, or approved by EMA or FDA
Rituximab is a medication that attacks certain cells of the immune system (B cells) and thereby reduces the production of harmful antibodies. In IgG4-related disease, it works by eliminating precisely those B cells that produce the problematic IgG4 antibodies.
Rituximab is administered intravenously (via an infusion) and is used more often when corticosteroids alone do not work well enough, or to limit long-term steroid use. Studies show that rituximab is effective in resolving inflammation and preventing recurrence.
**Known side effects** include reactions at the infusion site, flu-like symptoms, fatigue, and increased infection risk because certain immune cells are suppressed. Serious side effects are rare but possible.
A recent case discussion illustrates how rituximab can be used as a steroid-sparing agent, even after other treatments such as immune checkpoint inhibitors.
Mycophenolate mofetil (MMF)
ResearchediPositive results in clinical studies, not yet standard treatment
Mycophenolate mofetil is a medication that inhibits the proliferation of certain immune cells. It is used in some patient groups with IgG4-related disease as a aid in reducing corticosteroids or as an alternative when other medications do not work or are not well tolerated.
Although clinical experiences are positive, large-scale controlled studies are lacking that definitively establish how effective MMF is exactly. Therefore, this medication remains particularly relevant for selected patients and further validation.
**Known side effects** mainly involve gastrointestinal complaints (diarrhea, abdominal pain), changes in blood values (lower counts of certain white blood cells), and increased susceptibility to infection.
Azathioprine
ResearchediPositive results in clinical studies, not yet standard treatment
Azathioprine is a more classical immunosuppressor that is also used for other autoimmune diseases. In IgG4-related disease, it appears as supportive medication or steroid-sparing agent, especially in cases where rituximab is not available or not suitable.
Efficacy has not been demonstrated in large randomized studies, but clinical practice and smaller series suggest a role. Its use is therefore more 'investigated' than standard.
**Known side effects** include nausea, fatigue, skin rash, and reduced blood cell counts. Regular blood monitoring is necessary.
Biological therapies under investigation
ResearchediPositive results in clinical studies, not yet standard treatment ExperimentaliOngoing in study setting, outcome still unknown
Various studies are underway into new biological drugs for IgG4-related disease. These focus on other parts of the immune system:
- **Efgartigimod** (currently in clinical trial): This medication reduces certain antibodies in the blood. Studies are testing whether it is also effective in IgG4-related disease.
- **Rilzabrutinib** (currently in clinical trial): This agent inhibits signaling in certain immune cells. A 52-week study compares this therapy with placebo.
- **Lenalidomide** (currently in clinical trial): Originally developed for certain cancers, it is now being investigated as a possible immunomodulatory agent.
- **CAR-T cell therapy** (experimental, in trial): An approach where patients' own immune cells are modified outside the body to attack harmful cells, and then returned. This is still highly experimental and reserved for research.
These drugs are not available for regular use, but represent research efforts toward more targeted therapy.
Treatment of specific organ involvement
In addition to systemic (whole body) medications, local measures are sometimes used:
- **Peritonitis (mesenteritis)**: Monitoring and corticosteroid treatment; rituximab in severe cases.
- **Kidneys**: Intravenous corticosteroids and immunosuppressive agents; rituximab if response is inadequate.
- **Glandular involvement** (salivary glands, tears): Local steroids and systemic treatment depending on symptoms.
- **Nervous system**: Higher dose corticosteroids; rituximab in chronic forms.
Supportive care
Patients on long-term immunosuppression often receive additional medication:
- **Infection prophylaxis**: Preventive antibiotics or antivirals may be needed.
- **Bone strengthening**: With long-term steroid use, calcium supplements and vitamin D are recommended.
- **Monitoring**: Regular blood and imaging tests follow response to treatment and detect side effects.
Treatment of IgG4-related disease remains largely individualized. The physician will consider which organs are involved, how active the disease is, comorbidities, and previous medication responses. The goal is to control the disease with the least possible side effects.
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_This information never replaces a doctor's judgment. Always discuss your situation with your own healthcare provider._