Selective IgA deficiency
- Definition: most common primary immunodeficiency that is characterized by a near or total absence of serum and secretory IgA
- Pathophysiology: because of the deficiency of secretory IgA, infections can happen in respiratory tract and GI tract.
- Clinical features
- Often asymptomatic
- May manifest with sinusitis or respiratory infections (S. pneumoniae, H. influenzae), seen in childhood
- Chronic diarrhea, partially due to elevated susceptibility to parasitic infection (e.g. by Giardia lamblia)
- Associated with autoimmune diseases (e.g., gluten-sensitive enteropathy, inflammatory bowel disease, immune thrombocytopenia) and atopy
- Anaphylactic reaction to products containing IgA (e.g., intravenous immunoglobulin)
Tip
To prevent transfusion reactions, IgA-deficient patients must be given washed blood products without IgA or obtain blood from an IgA-deficient donor.
- Diagnosis
- Decreased serum IgA levels (< 7 mg/dL)
- Normal IgG and IgM levels
- False-positive pregnancy tests