For patients and their doctors
The five red flags
Researchers across Europe agreed on five signs that should make a doctor think of IgG4-related disease and refer to a specialist. These are not a test, and they cannot tell you whether you have the disease. They are a starting point for a conversation with your doctor. If several feel familiar, that is a reason to ask, not an answer.
A note before you read. These are not diagnostic criteria and not a checklist to score yourself against. They are expert-opinion signals that should prompt a specialist review. Only a doctor can put them together with your history, your examination, and the right tests.
Swelling in one or more organ or area
The disease often shows up as swelling or enlargement — in glands, organs, or surrounding tissues — sometimes in more than one place, and sometimes appearing in different places over time.
Source: Della-Torre et al., The Lancet Rheumatology, 2025
The pancreas or bile ducts are involved
Inflammation of the pancreas or of the bile ducts (the small tubes that carry bile from the liver) is one of the most common patterns. It is also where IgG4-related disease is most often mistaken for something else, including cancer.
Source: Della-Torre et al., The Lancet Rheumatology, 2025
A raised level of IgG4 in the blood
A blood test can show a higher-than-usual level of IgG4, a type of antibody. On its own this does not confirm the disease, and a normal level does not rule it out — but a raised level is one signal among others worth weighing.
Source: Della-Torre et al., The Lancet Rheumatology, 2025
Tissue findings under the microscope
When a small sample of affected tissue (a biopsy) is examined, certain patterns point toward the disease — including a particular kind of immune-cell build-up rich in IgG4-producing cells.
Source: Della-Torre et al., The Lancet Rheumatology, 2025
A specific kind of vein inflammation
A characteristic inflammation of small veins, called obliterative phlebitis, is seen in some tissue samples. For specialists, it is one of the more telling signs.
Source: Della-Torre et al., The Lancet Rheumatology, 2025
Where this comes from
Della-Torre E, Talarico R, Ballarín J, et al. Identification of red flags for IgG4-related disease: an international European Reference Network framework. The Lancet Rheumatology, 2025.
These red flags come from expert agreement and are still being studied. They are meant to help doctors recognise the disease sooner. They are not a diagnosis. Always take them to a specialist.
If this feels familiar, the next step is a conversation with a doctor who knows this disease.
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