• 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