IgG4-RD can be hard to diagnose. There isn’t one single test that confirms it. Doctors usually look at a combination of the following:

1. Blood Tests

• IgG4 level – This may be high in many people with IgG4-RD, but not always. A normal level does not rule it out.
• IgG1, IgE, and complement levels (C3 and C4) – These can also show changes linked to inflammation.
• Organ-specific tests – Doctors may check how the liver, kidneys, pancreas, or other organs are working.

2. Imaging Scans

• CT scan (Computed Tomography) – Shows organ enlargement or masses
• MRI (Magnetic Resonance Imaging) – Helpful for looking at soft tissue or brain involvement
• Ultrasound – Often used to check for swelling in organs like the salivary glands or kidneys
• PET scan (Positron Emission Tomography) – Helps show active inflammation

3. Biopsy

A biopsy is when a small sample of tissue is taken from a swollen or affected area. Doctors look at the tissue under a microscope for signs of IgG4-RD, such as:

• High numbers of IgG4-positive plasma cells
• Storiform (whorled) fibrosis
• Obliterative phlebitis (veins blocked by inflammation)

Not all biopsies show all of these features, but together they help confirm the diagnosis.

Misdiagnosis is Common

Because symptoms can look like other diseases, IgG4-RD is often misdiagnosed as:

• Cancer (most common)
• Sjögren’s disease
• Sarcoidosis
• Infections
• Other autoimmune conditions

The goal of treatment is to control the disease, reduce inflammation, and prevent long-term organ damage.

Common Treatments:

• Steroids (such as prednisone) – Often the first treatment to reduce inflammation quickly
• Immunosuppressive medications (such as azathioprine or mycophenolate mofetil) – May be used to keep the disease under control
• Biologics (like uplizna and rituximab) – Used for patients who don’t respond well to steroids or need longer-term treatment

IgG4-RD usually requires a team of doctors, depending on which parts of the body are affected. This may include:

• Rheumatologist – Expert in immune and inflammatory diseases
• Gastroenterologist – For pancreas, liver, or bile duct involvement
• Nephrologist – For kidney involvement
• Pulmonologist – If the lungs are affected
• Ophthalmologist – For eye-related problems
• Radiologist & Pathologist – Help interpret scans and biopsies
• Primary care doctor – Helps coordinate care

These doctors work together to create a treatment plan that fits your needs.

Common treatments include:

• Steroids (like prednisone) to reduce inflammation
• Immune-suppressing medicines (such as azathioprine or mycophenolate)
• Biologics (like uplizna and rituximab) for long-term care

Note: As of April 3, 2025, the FDA approved a treatment called Uplizna for IgG4-RD. Learn more at uplizna.com

Visit aiarthritis.org/Equation to download our Mystery Patient Guide and listen to Talk Show episodes

Find more resources at:

• Igg4ward.org – Patient Advocacy Organization – Education, resources and Find a Doctor
• igg4rdoutloud.com – Tools and care planning
• uplizna.com – Info on the FDA-approved treatment