IgG4 related disease

IgG4-related disease is a rare autoimmune condition where the immune system becomes overactive and mistakenly attacks healthy tissues in the body. It can affect many organs, including the pancreas, salivary glands, bile ducts, kidneys, and lymph nodes. This disease is called “IgG4-related” because it is associated with increased levels of a specific antibody called IgG4. The condition can cause inflammation, swelling, and scarring, leading to a range of symptoms depending on which part of the body is involved. Early diagnosis and treatment are important to prevent permanent damage to the affected organs.

What is IgG4?

IgG4 is a type of protein called an immunoglobulin, or antibody, that is produced by your immune system. Antibodies help your body fight infections by recognizing and attacking bacteria, viruses, and other foreign invaders. IgG4 is one of several types of immunoglobulins found in your blood, and it usually plays a role in regulating immune system responses to avoid overreacting to harmless substances.

How is IgG4 different from other immunoglobulins?

There are five main types of immunoglobulins: IgG, IgA, IgM, IgE, and IgD. IgG is the most common type, and it is further divided into four subtypes: IgG1, IgG2, IgG3, and IgG4. IgG4 is unique because it does not activate certain parts of the immune system as strongly as other immunoglobulins. This feature makes IgG4 important for reducing inflammation and preventing unnecessary immune reactions. However, in some conditions, the body produces too much IgG4, which can lead to disease.

What conditions are associated with increased IgG4 production?

Excess IgG4 is associated with a condition called IgG4-related disease. This is a rare autoimmune condition where the immune system mistakenly attacks normal tissues in the body. It can affect many different organs, including the pancreas, salivary glands, bile ducts, kidneys, and lymph nodes. Increased IgG4 can also be seen in other conditions, such as certain types of cancer and infections, but in these cases, it is not the cause of the disease.

Specific IgG4-related conditions include:

• IgG4-related sialadenitis: Swelling and inflammation of the salivary glands.
• IgG4-related pancreatitis: Inflammation of the pancreas, often causing abdominal pain and digestive issues.
• IgG4-related cholangitis: Inflammation and narrowing of the bile ducts, which can lead to jaundice.
• IgG4-related retroperitoneal fibrosis: Thickening and scarring of tissues in the area behind the abdominal cavity.
• IgG4-related orbital disease: Inflammation around the eyes, leading to swelling and vision problems.
• IgG4-related nephritis: Inflammation of the kidneys that can cause impaired kidney function.

What are the symptoms of IgG4-related disease?

The symptoms of IgG4-related disease depend on which part of the body is affected. Common symptoms include swelling or masses that may be mistaken for cancer, pain, or dysfunction of the affected organ. For example, if the salivary glands are involved, a person may notice swelling of the face or difficulty swallowing. When the pancreas is affected, symptoms may include abdominal pain or yellowing of the skin and eyes (jaundice).

How do doctors test for IgG4-related disease?

Doctors use a combination of blood tests, imaging studies, and tissue biopsies to diagnose IgG4-related disease. Blood tests can measure the levels of IgG4 in your blood, which are often elevated in this condition. Imaging studies, such as CT or MRI scans, can show swollen or damaged organs. A biopsy, where a small piece of tissue is taken and examined under a microscope, is usually required to confirm the diagnosis. The pathologist will look for specific features that suggest IgG4-related disease and may also test the tissue for IgG4 using a special technique called immunohistochemistry.

What are some of the microscopic features of IgG4-related disease?

Under the microscope, tissues affected by IgG4-related disease often show inflammation and scarring. The inflammation is made up of many immune cells, including plasma cells, which produce antibodies like IgG4. A key feature of IgG4-related disease is a large number of plasma cells producing IgG4. The pathologist can confirm this by performing immunohistochemistry to stain the tissue for IgG4. Another feature is fibrosis, or scarring, which can cause the affected tissue to become stiff and lose its normal function.

Understanding the role of IgG4 in your pathology report can provide important insights into your diagnosis and guide your treatment plan. If you have questions about your pathology report, talk to your doctor for more information.