STEPTRACKERIMMUNOLOGY | IMMUNE DEFECTS | RAPID-FIRE REVIEW

Defect → Infection & Disease

Every immunodeficiency and complement defect in one table — the defect, its infections or disease, the test that confirms it and the page that explains it.

FOCUS ON
Sort first by arm: B cell (encapsulated, enterovirus, Giardia; after 6 months) · T cell/combined (viruses, fungi, Pneumocystis; first months) · phagocyte (abscesses, S aureus, Aspergillus) · complement (encapsulated, Neisseria, lupus-like, angioedema) · cytokine axis (mycobacteria, Candida, S aureus). Then use the extra-immune clue: tetany and heart defect (DiGeorge), eczema with small platelets (Wiskott-Aldrich), ataxia (ATM), retained teeth (STAT3), albinism (Chédiak-Higashi), cord separation (LAD). Full pages: 6.01–6.04.
DEFECT
INFECTIONS / DISEASE
CONFIRMING TEST
PAGE
BTK (XLA)
Encapsulated bacteria, enteroviral encephalitis, Giardia; absent tonsils
No CD19⁺ cells, all Ig ↓
6.01
CVID
Sinopulmonary, bronchiectasis, autoimmunity, lymphoma
↓ IgG/IgA, poor vaccine titers
6.01
Selective IgA
Mostly silent; Giardia, celiac, transfusion anaphylaxis
↓ IgA alone
6.01
CD40L (X-linked hyper-IgM)
Pneumocystis, Cryptosporidium, encapsulated bacteria
↑ IgM, ↓ IgG/IgA/IgE
6.01
22q11.2 (DiGeorge)
Viral/fungal infections, tetany, conotruncal defects
↓ T cells, ↓ Ca²⁺, FISH/microarray
6.02
γc, JAK3, ADA, RAG (SCID)
Thrush, Pneumocystis, chronic diarrhea, live-vaccine infections
Low TRECs, absent T cells
6.02
WAS (Wiskott-Aldrich)
Infections, eczema, bleeding, lymphoma
Small platelets, ↓ IgM, ↑ IgA/IgE
6.02
ATM (ataxia-telangiectasia)
Sinopulmonary infections, ataxia, lymphoma
↑ AFP, ↓ IgA
6.02
STAT3 (hyper-IgE)
Cold S aureus abscesses, Candida, pneumatoceles
↑↑ IgE, eosinophilia
6.02
IL-12R / IFN-γR
Disseminated mycobacteria, Salmonella
Cytokine pathway testing
6.02
AIRE (APS-1)
Chronic Candida, hypoparathyroidism, Addison
Autoantibodies to IL-17/IL-22
1.03
CD18 (LAD 1)
Omphalitis, infections without pus
↓ CD18 on flow, neutrophilia
6.03
NADPH oxidase (CGD)
Catalase ⁺: S aureus, Serratia, Burkholderia, Nocardia, Aspergillus
Abnormal DHR
6.03
LYST (Chédiak-Higashi)
Pyogenic infections, albinism, neuropathy, HLH
Giant granules
6.03
C1q, C2, C4
Lupus-like disease, encapsulated
↓ CH50
6.03
C3
Severe pyogenic infections, GN
↓ CH50 and AH50
2.02
C5–C9
Recurrent Neisseria
↓ CH50 and AH50
2.02
C1-INH
Hereditary angioedema
↓ C4, ↓ C1-INH level/function
2.02
PIGA (PNH)
Hemolysis, thrombosis, cytopenias
Flow: ↓ CD55/CD59
2.02
FOXP3 (IPEX) · FAS (ALPS)
Enteropathy, diabetes, eczema · lymphoproliferation, cytopenias
Genetic testing · ↑ double-negative T cells
5.01
Asplenia
Pneumococcus, Hib, meningococcus, Capnocytophaga, Babesia
Howell-Jolly bodies
1.01

Mechanism — matching organism to defense

CapsuleNeeds antibody + complement + spleen
Inside cellsNeeds T cells, IFN-γ, macrophages
Pyogenic, fungal hyphaeNeed neutrophils
NeisseriaNeeds the MAC

The extra-immune clue

CLUE
SYNDROME
GENE
Tetany + truncus
DiGeorge
22q11.2
Eczema + small platelets
Wiskott-Aldrich
WAS
Ataxia + telangiectasias
A-T
ATM
Retained baby teeth
Hyper-IgE
STAT3
Silvery hair
Chédiak-Higashi
LYST
Late cord separation
LAD 1
ITGB2

How it's tested

COMMON CONFUSIONHyper-IgE (STAT3; eczema, abscesses, high IgE) vs Wiskott-Aldrich (eczema, bleeding, small platelets) vs atopic dermatitis (eczema only).
THE TRAPMany of these are X-linked (XLA, CD40L hyper-IgM, γc SCID, WAS, most CGD, properdin) — think of them first in boys.
YOUR APPROACHArm of immunity → extra-immune clue → confirming test → page.

If you see… think…

X-linked defects → XLA, CD40L, γc SCID, WAS, CGD (gp91), properdin
Defect with Howell-Jolly bodies → asplenia
DHR abnormal → CGD
TRECs low on newborn screen → SCID
↑ AFP with immunodeficiency → ataxia-telangiectasia
↓ C4 with episodic swelling → C1-INH deficiency
Encapsulated infections, normal Ig and complement → asplenia or specific antibody deficiency
Candida + endocrine failure → AIRE
Mycobacteria after BCG with normal CD4 count → IL-12/IFN-γ axis
No pus, high WBC → LAD