Primary immunodeficiency syndromes - key syndromes and defects (XLA, CVID, DiGeorge, CGD)
Core concept
- Classify by the arm that has failed - the infection pattern names the defect
| Arm | Typical organisms | Onset |
|---|---|---|
| Antibody (B cell) | Encapsulated bacteria - pneumococcus, H. influenzae, Neisseria; enterovirus, Giardia, Campylobacter, mycoplasma | After 6 months, when maternal IgG wanes |
| T cell / combined | Opportunists - PJP, CMV, EBV, candida, Cryptosporidium, disseminated BCG/live vaccines, mycobacteria | First months of life |
| Phagocyte | Catalase-positive organisms - S. aureus, Serratia, Burkholderia, Nocardia, Aspergillus | Early, with abscesses and poor wound healing |
| Complement | Neisseria (terminal), encapsulated (early classical); SLE-like autoimmunity | Any age |
- Warning signs: >=2 pneumonias or >=8 otitis in a year, failure to thrive, deep abscess, persistent thrush after 1 y, need for IV antibiotics to clear infection, family history, unexplained bronchiectasis in an adult
- Most adult-diagnosed primary immunodeficiency is CVID - and the first presentation is often bronchiectasis, autoimmune cytopenia or granulomatous disease, not infection
3 more sections, plus exam facts
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