From the Guidelines
Increased Immunoglobulin G (IgG) levels are typically caused by autoimmune hepatitis (AIH) and allergen immunotherapy.
Causes of Increased IgG Levels
- Autoimmune Hepatitis (AIH): Elevated IgG levels, especially in the absence of cirrhosis, are a distinctive feature of AIH 1. A selectively elevated IgG in the absence of IgA and IgM elevation is particularly suggestive of AIH.
- Allergen Immunotherapy: Increases in allergen-specific IgG antibody titers are associated with immunotherapy, although they are not predictive of the duration and degree of efficacy of immunotherapy 1.
Key Points
- Increased IgG levels are found in approximately 85% of patients with AIH, even in the absence of cirrhosis 1.
- The presence of high IgG levels is a very distinctive feature of AIH, with IgA and IgM levels usually being normal 1.
- Allergen immunotherapy is associated with a change toward a T H 1 CD41 cytokine profile and the generation of CD41CD251 regulatory T lymphocytes, which can lead to increased IgG levels 1.
- The relationship between increased IgG levels and the clinical response to immunotherapy is not completely understood and requires further research 1.
From the Research
Causes of Increased Immunoglobulin G (IgG) Levels
- High levels of IgG are associated with a range of diseases and/or poor health behaviors, such as autoimmune diseases, chronic infection, HIV, and excessive alcohol consumption 2
- Elevated serum IgG levels are found in patients with chronic liver disease (CLD) of different causes, particularly in those with decompensated cirrhosis 3
- IgG4-related disease (IgG4-RD) is associated with elevated serum IgG4 levels, and a serum IgG4 of ≥2.8 g/l is useful in distinguishing between IgG4-RD and non-IgG4-RD diagnoses 4
- Adverse effects of IgG therapy, such as infusion-related reactions, renal dysfunction, and thromboembolic events, can also lead to increased IgG levels 5
- Isolated elevations of each of the four IgG subclasses are associated with various diseases, including autoimmune pancreatitis, rheumatoid arthritis, hepatitis C, and hypothyroidism 6
Disease Associations
- Autoimmune diseases: elevated IgG levels are associated with autoimmune diseases such as autoimmune pancreatitis, rheumatoid arthritis, and autoimmune hepatitis 2, 3, 6
- Chronic infections: elevated IgG levels are associated with chronic infections such as HIV and hepatitis C 2, 6
- Liver disease: elevated IgG levels are associated with chronic liver disease, particularly in those with decompensated cirrhosis 3
- IgG4-related disease: elevated IgG4 levels are associated with IgG4-RD, a group of immune-mediated disorders 4