IgG4-Related Disease

Causes & Risk Factors

The exact cause of IgG4-related disease is not fully understood, but certain patterns are recognized:

•  More commonly diagnosed in middle-aged and older adults.

•  More frequently affects men than women, though it can occur in either sex.

•  Believed to involve an abnormal immune-mediated inflammatory process, though the precise trigger is not well established.

•  Can affect a single organ or multiple organs simultaneously or sequentially over time.

Symptoms & When to Test

Symptoms of IgG4-related disease depend heavily on which organ or organs are affected, and can develop gradually.

•  Painless swelling of affected organs — such as salivary or lacrimal glands, lymph nodes, or the pancreas

•  Jaundice or abdominal symptoms, when the pancreas or biliary tract is involved

•  Kidney dysfunction, when the kidneys are involved

•  Symptoms specific to whichever organ system is affected, which can make the condition difficult to recognize without specific consideration

When Should You Consider Testing?

Testing is generally considered when there is unexplained swelling or dysfunction of one or more of the organs commonly associated with IgG4-related disease, particularly when other causes have been considered and a systemic, immune-mediated process is suspected.

Why Tests Are Combined

Serum IgG4 provides supportive evidence when elevated, but because IgG4-related disease requires a combination of clinical, serological, radiological, and often histopathological features for diagnosis, no single blood test — including IgG4 — can confirm the diagnosis alone.

Elevated IgG4 can also occur in other conditions, meaning an elevated result increases suspicion but must be interpreted together with imaging findings (showing characteristic organ involvement) and, in many cases, tissue biopsy showing the characteristic pathological features.

Because IgG4-related disease can mimic other conditions — including certain cancers, depending on the organ involved — this combined, multi-step diagnostic approach is important both to confirm the diagnosis and to exclude other serious conditions that require different management.

Tests Available at NPL

Most allergy and immunology blood tests do not require fasting. However, some tests ordered at the same time may have specific preparation requirements. Please follow the instructions provided by your doctor or NPL.

Home Sample Collection

Blood testing (serum IgG4 and total immunoglobulins) can be arranged through NPL's standard home sample collection service.

If tissue biopsy is required to confirm the diagnosis (based on your specialist's assessment), this is performed as a specialist procedure at a hospital or clinic, not through home collection.

Imaging studies required for diagnosis are arranged separately through your treating hospital or imaging center.

NPL processes the biopsy tissue for histopathology once obtained by your specialist, in coordination with your treating team.

When to See a Doctor

•  Unexplained, painless swelling of salivary glands, lacrimal glands, or lymph nodes

•  Unexplained pancreatic or biliary symptoms, including jaundice

•  Unexplained kidney dysfunction with other suggestive features

•  Multiple organ involvement without a clear alternative explanation