IgG4-related disease
An uncommon disease in which the immune system drives inflammation and scarring that can affect many organs — classically the pancreas, bile ducts and salivary glands — often forming tumour-like swellings. A raised blood IgG4 supports it, and it usually responds well to treatment with steroids.
What it is
IgG4-related disease is a fibro-inflammatory condition, recognised as a single entity only relatively recently, in which affected tissues become infiltrated by immune cells rich in IgG4 and develop a characteristic pattern of inflammation and dense scarring (fibrosis). This often produces firm, tumour-like swelling or enlargement of the organs involved, which is why it can be mistaken for cancer. It can affect almost any part of the body, but has classic targets: the pancreas (type 1 autoimmune pancreatitis), the bile ducts (IgG4-related sclerosing cholangitis), the salivary and tear glands (causing painless enlargement), the kidneys, the lungs, the aorta and the retroperitoneum (where scarring can wrap around and obstruct structures). Several organs are often involved at once, or over time. Many people have a raised blood IgG4 level, which supports the diagnosis, but the level can be normal, and a mild rise can occur in other conditions — so the diagnosis depends on the pattern of organ involvement, imaging, the IgG4 level and, crucially, a biopsy showing the typical tissue changes. The key point is that, despite mimicking cancer and other serious diseases, IgG4-related disease usually responds well to treatment that calms the immune system, typically steroids, making its recognition important.
Key lab markers
- IgG4 — often markedly raised; the characteristic blood marker, though it can be normal.
- Total IgG — may be raised.
- Alkaline phosphatase and GGT — raised if the bile ducts are involved (a cholestatic pattern).
- Amylase and lipase — can be raised with pancreatic involvement.
- Kidney function — checked, as the kidneys can be affected.
- Biopsy — showing the typical IgG4-rich tissue changes is central to the diagnosis.
Symptoms
- Painless swelling or enlargement of organs or glands (salivary, tear glands)
- Jaundice and pale stools if the bile ducts are involved
- Abdominal discomfort or a pancreatic 'mass'
- Fatigue and weight loss
- Symptoms depending on which organs are affected (kidneys, lungs, aorta)
- Often found while investigating a suspected cancer that turns out to be this instead
Related lab panels
When to discuss with a doctor
IgG4-related disease is a specialist-managed condition, considered when there is unexplained inflammation, scarring or tumour-like swelling of the pancreas, bile ducts, salivary or tear glands, kidneys or other organs — particularly when several organs are involved or a suspected cancer does not behave as expected. A raised blood IgG4 supports it, but the diagnosis rests on the whole picture and usually a biopsy. It matters because it can closely mimic cancer, yet typically responds well to treatment, so getting the diagnosis right avoids both missed treatment and unnecessary cancer surgery. Care and follow-up are led by a specialist, often across several disciplines. Mediora.AI can highlight a raised IgG4 or a cholestatic liver pattern that should prompt evaluation, but the diagnosis and treatment belong with your specialist team.