An elevated Immunoglobulin A (IgA) level, usually detected during a blood test, signifies a heightened response by the body’s immune system. IgA is an antibody produced to identify and neutralize foreign invaders like bacteria and viruses. A high IgA measurement is not a diagnosis itself, but a marker indicating the immune system is actively engaged in a significant process. The underlying cause can range from a common, temporary infection to a complex, chronic systemic condition.
Understanding the Function of IgA
IgA is the second most common antibody found in the bloodstream, but it is the most abundantly produced antibody in the entire body. The primary role of IgA is to safeguard the body’s mucosal surfaces, which are the moist linings of the respiratory, gastrointestinal, and genitourinary tracts. These mucosal surfaces represent the largest area of potential entry for pathogens, so IgA forms a protective barrier.
The antibody exists in two main forms that reflect its function and location. In the blood serum, IgA is predominantly a single-unit structure known as monomeric IgA. Conversely, in secretions like saliva, tears, mucus, and breast milk, IgA is primarily found as a double-unit structure called dimeric IgA, also known as secretory IgA (sIgA).
The dimeric form is connected by a joining chain and a protective secretory component, making it resistant to degradation by digestive enzymes and harsh environments. This resilience allows secretory IgA to effectively bind to pathogens in the gut and airways. This prevents them from adhering to and invading host cells, a process called immune exclusion.
Systemic Conditions Causing Elevated IgA
Elevated IgA levels found in the serum often point toward chronic, systemic conditions triggering a persistent immune response. One significant category involves liver diseases, particularly those leading to cirrhosis, such as alcoholic liver disease or chronic hepatitis. In these conditions, the liver’s impaired ability to clear IgA from the circulation causes the antibody to accumulate in the bloodstream.
Several autoimmune conditions can also cause a polyclonal increase in serum IgA due to ongoing, widespread inflammation. For instance, Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA) sometimes present with elevated IgA. This reflects the chronic immune dysregulation that drives the overproduction of antibodies.
Specific kidney disorders are directly linked to abnormal IgA complexes and are often associated with elevated serum levels. IgA Nephropathy (Berger’s disease) occurs when abnormal IgA complexes deposit in the filtering units of the kidneys (glomeruli), causing inflammation and potential damage. A related condition is IgA Vasculitis (Henoch-Schönlein purpura), where IgA deposits in small blood vessels throughout the body, commonly affecting the skin, joints, and kidneys.
Mucosal and Infectious Causes of High IgA
The most frequent reasons for an elevated IgA result are localized to the mucosal surfaces and represent a robust immune defense. Acute infections, especially those affecting the respiratory tract (e.g., bronchitis) or the gastrointestinal tract (e.g., gastroenteritis), cause a rapid ramp-up in secretory IgA production. This surge can result in a temporary spillover of IgA into the systemic circulation, leading to a measured elevation in the blood test.
Chronic inflammatory conditions of the digestive system also drive IgA levels upward due to constant immune activity within the gut wall. Inflammatory Bowel Disease (IBD), including Crohn’s disease and ulcerative colitis, involves persistent inflammation of the intestinal lining, an area rich with IgA-producing cells. Similarly, Celiac disease involves the production of specific IgA antibodies against tissue transglutaminase (tTG), contributing to the overall rise in total serum IgA.
The IgA system in the gut constantly works to maintain balance with the trillions of bacteria that make up the microbiome. Any sustained disruption or irritation to this large surface area forces the immune system to generate more IgA. This increase reflects the body’s effort to contain threats and maintain the integrity of the mucosal barrier.
Diagnostic Follow-Up and Interpretation
An elevated IgA level must be viewed as a signal, not a definitive diagnosis, requiring a thorough clinical investigation. The result must be correlated with a patient’s specific symptoms, medical history, and any other abnormalities found on a complete blood count or metabolic panel. An isolated high IgA finding in an otherwise healthy individual may be a transient response to a recent minor illness and may warrant only a re-test in a few months.
If the elevation is significant or persistent, a physician will typically order targeted follow-up tests. To rule out liver involvement, liver function tests (LFTs) will be performed. If kidney issues are suspected, a urinalysis is often conducted to look for blood or protein in the urine, followed by a urine protein-to-creatinine ratio.
Further blood work may include an autoantibody panel to screen for autoimmune diseases or specific IgA subtyping for Celiac disease antibodies. In some cases, a serum protein electrophoresis may be ordered to determine if the IgA elevation is polyclonal (many different types of IgA are elevated) or monoclonal (suggesting a plasma cell disorder). Treatment focuses on addressing the underlying condition causing the immune system activity, not on treating the elevated IgA level itself.