From the Guidelines
Low IgA, or Immunoglobulin A deficiency, is a condition where the body produces insufficient amounts of IgA antibodies, and it is diagnosed when serum IgA levels are less than 7 mg/dL, with normal serum IgG and IgM levels, and other causes of hypogammaglobulinemia have been excluded 1. This condition affects approximately 1 in 300 to 700 white subjects in the United States, and it is relatively rare in Asian populations. Many individuals with low IgA are asymptomatic, but some may experience recurrent respiratory and gastrointestinal tract infections, atopy, autoimmune diseases, celiac disease, and malignancy.
- The diagnosis of low IgA is based on serum IgA levels, and it is essential to use methods capable of detecting IgA concentrations of less than 7 mg/dL to determine whether IgA is truly absent or present at very low concentrations.
- Patients with low IgA should be monitored over time for the occurrence of complications, and management focuses on treating infections promptly when they occur, using antibiotics when necessary.
- Preventive measures include good hygiene practices, avoiding known allergens, and in some cases, immunoglobulin replacement therapy for those with severe or recurrent infections.
- The condition is often genetic and results from a failure in the normal development of B cells that would typically produce IgA antibodies.
- While most people with low IgA lead normal lives, regular medical follow-up is recommended to monitor for complications, and some patients with low IgA may develop common variable immunodeficiency (CVID) later in life 1.
- It is also important to note that patients with IgA deficiency are considered to be at risk for anaphylactic reactions to blood products, and practices vary, but some centers will transfuse products from IgA-deficient donors for IgA-deficient recipients or wash cells before they are transfused 1.
From the Research
Definition of Low IgA
Low IgA, also known as selective IgA deficiency (SIgAD), is a primary immunodeficiency characterized by a decreased serum level of IgA in the presence of normal levels of other immunoglobulin isotypes 2, 3.
Clinical Implications
Individuals with low IgA may be asymptomatic or present with various clinical complications, including:
- Increased risk of sinopulmonary infections with bacteria and viruses
- Gastrointestinal infections with a predilection for Giardia lamblia
- Autoimmune diseases such as systemic lupus erythematosus, hyper- and hypo-thyroidism, Type 1 diabetes, and celiac disease
- Rarely, malignancy 2, 3, 4
Diagnosis and Differentiation
SIgAD must be differentiated from IgA deficiency that may be seen with IgG2 or IgG4 deficiency, specific antibody deficiency, or as an early manifestation prior to a diagnosis of common variable immunodeficiency 2. Secondary IgA deficiency is increasingly recognized and may be due to medications, infections, or malignancies 2.
Functions of IgA
IgA is the most abundant antibody isotype produced in the body, with subclass IgA1 mainly found in the blood circulation and subclass IgA2 dominant in mucosal secretions 3. Secretory IgA appears to have prime importance in immune exclusion of pathogenic microorganisms and maintenance of intestinal homeostasis.
Treatment and Monitoring
Patients with SIgAD should be monitored at regular intervals and educated to be aware of particular complications 2. Prophylactic antibiotics may be indicated in some cases, and very rarely, supplemental IgG infusions may be considered 2, 5. Close monitoring for malignancy should be strongly considered for patients with IgE deficiency and other isotype deficiencies 5.