CF vs PCD vs Immunodeficiency Cheatsheet
Key Concept: Situs inversus + bronchiectasis + sinusitis = Kartagener syndrome (PCD subtype). CF: CFTR mutation, pancreatic insufficiency, elevated sweat chloride. IgA deficiency: usually mild, no situs inversus. CVID: presents >20yo, Giardia, pan-low immunoglobulins.
| Diagnosis | Key Features |
|---|
| Cystic Fibrosis |
- CFTR gene mutation (chromosome 7)
- Elevated sweat chloride (>60 mEq/L) is diagnostic
- Pancreatic insufficiency → fat malabsorption + fat-soluble vitamin deficiency
- Nasal polyps
- Digital clubbing
- Meconium ileus in neonates
- Normal heart position (situs solitus)
- Treated with CFTR modulators (ivacaftor / elexacaftor-tezacaftor-ivacaftor)
|
| Primary Ciliary Dyskinesia |
- Dynein arm defect → impaired ciliary motility
- Bronchiectasis + chronic sinusitis + male infertility
- Situs inversus in ~50% (Kartagener syndrome = PCD + situs inversus)
- Normal sweat chloride
- Normal pancreatic function
- Nasal nitric oxide very low (screening test)
- Diagnosed by electron microscopy of cilia or genetic testing
|
| IgA Deficiency |
- Most common primary immunodeficiency
- Often asymptomatic; mild recurrent sinopulmonary infections if symptomatic
- No situs inversus
- Selective IgA deficiency; normal IgG and IgM
- Anaphylaxis risk with IgA-containing blood transfusion
|
| CVID |
- Pan-hypogammaglobulinemia (IgG + IgA + IgM all low)
- Presents in 2nd–3rd decade (young adults)
- Recurrent infections with encapsulated bacteria (S. pneumoniae, H. flu)
- Giardia lamblia intestinal infection (characteristic)
- Treated with IV immunoglobulin (IVIG)
|