From the Guidelines
Low Immunoglobulin A (IgA) levels, also known as Selective IgA Deficiency (SIGAD), indicate a condition where the body does not produce enough IgA antibodies, which are crucial for fighting infections, particularly in the mucosal areas such as the respiratory, gastrointestinal, and genitourinary tracts 1.
Key Points
- Diagnosis of SIGAD is made 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.
- Clinical manifestations of SIGAD can include respiratory and gastrointestinal tract infections, atopy, autoimmune diseases, celiac disease, and malignancy, although many patients are asymptomatic 1.
- Management of SIGAD involves monitoring for complications and may include IgG replacement therapy, antibiotics, and vigilance for autoimmune diseases 1.
- Laboratory findings for SIGAD typically show absent or very low IgA levels, with normal IgG and IgM levels, and normal or low vaccine response 2.
- Prevalence of SIGAD is estimated to be around 1 in 300 to 700 in white subjects in the United States, with a higher prevalence in males and a family history of SIGAD or Common Variable Immunodeficiency (CVID) in 20-25% of cases 1.
From the Research
Definition of Low Immunoglobulin A (IgA)
- Low Immunoglobulin A (IgA) is defined as a level of 0.07g/l after the age of four years in the absence of IgG and IgM deficiencies 3.
- IgA deficiency is the most common primary immunoglobulin deficiency, with a prevalence of around one in 500 in Caucasians, whereas it is very uncommon in some Asian populations 4.
Clinical Manifestations of Low IgA
- Patients with IgA deficiency may present with recurrent infections of the respiratory and gastrointestinal tracts, allergic disorders, and autoimmune manifestations 5.
- The most prevalent clinical manifestations of IgA deficiency include infections (64.8%), followed by allergic diseases (26.16%) and autoimmunity (22.0%) 6.
- Common infections associated with IgA deficiency include respiratory tract infection, fungal infection, and gastrointestinal infection 6.
- Autoimmune diseases associated with IgA deficiency include celiac disease, inflammatory bowel disease, and rheumatoid arthritis 6.
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 in mucosal secretions 5.
- Secretory IgA plays a critical role in immune exclusion of pathogenic microorganisms and maintenance of intestinal homeostasis 5.
Diagnosis and Treatment
- IgA deficiency is often diagnosed coincidentally, and most individuals with IgA deficiency are asymptomatic 4, 5.
- There is no specific treatment for patients with symptomatic IgA deficiency, and antibiotics are prescribed in those with acute infections 4.
- Patients with IgA deficiency should undergo periodic assessments to inspect for new clinical complications during follow-up 6.