Overview of the diagnosis of IgG₄-related disease

Diagnosis of immunoglobulin G4 (IgG₄₎–related disease can be difficult and is usually based on a combination of:

• clinical features
• serologic features—an elevated serum IgG₄ concentration may be seen in 20 to 66% of people
• imaging—utility of imaging will depend on the person’s presentation and pretest probability
• histopathological analysis of a tissue biopsy—approximately 60% of people may have a biopsy-proven diagnosisWallace, 2020.