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Primary Lymphoid Organs to Lymph Node Structural Diagram7Topics
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Introduction to Lymphatic Drainage to Lymph Node Palpability and Right Lymphatic Duct6Topics
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Spleen Structure Overview to Thymus-Related Conditions6Topics
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Components and Mechanism of Immunity to Understanding Immune Privilege4Topics
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MHC I and II: Introduction and Loci to DQ8, DR3, DR49Topics
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Functions of Natural Killer Cells to Major Functions of T Cells3Topics
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T Cell Development: Bone Marrow & Thymus to Regulatory T Cells and Autoimmunity6Topics
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T-cell Activation: Antigen Presentation to B-cell Activation: Co-stimulation, Class Switching, and Maturation4Topics
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Antibody Structure and Function to Antibody Diversity and Specificity4Topics
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Introduction to Immunoglobulin Isotypes to Thymus-Dependent Antigens7Topics
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Introduction to Complement System to Convergence and MAC Formation9Topics
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Early Complement Deficiencies to PNH: Hemolysis & Thrombosis4Topics
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Interleukin-1: Macrophage Secretion and Acute Response to IL-10 and IL-13: Immune Regulation and IgE Production7Topics
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Respiratory Burst Introduction to Interferons Clinical Use & Side Effects5Topics
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T Cell Surface Proteins to Examples of Passive and Active Immunity4Topics
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Live Attenuated Vaccines: Description to mRNA Vaccine8Topics
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Overview of Hypersensitivity Types to Type II: Cellular Dysfunction & Clinical Examples6Topics
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Type III Hypersensitivity: Mechanism & Examples to Type IV Hypersensitivity: Examples & Tests5Topics
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Allergic and Anaphylactic Transfusion Reactions to Delayed Hemolytic Transfusion Reaction5Topics
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Autoantibodies in Neuromuscular and Systemic Diseases to Autoantibodies in Metabolic, Hematologic, and Renal Disorders5Topics
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Bruton's Agammaglobulinemia to Chronic Mucocutaneous Candidiasis7Topics
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Severe Combined Immunodeficiency (SCID) to Chronic Granulomatous Disease7Topics
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Intro to Immunodeficiency & T-Cell Bacterial Infections to Parasitic Infections & Key Deficiency Note5Topics
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Hyperacute Transplant Rejection to Histology of Transplant Rejection5Topics
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Immunosuppressants: Definition and Risks to Sirolimus & Basiliximab: Clinical Aspects5Topics
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Azathioprine to Immunotherapy: Interleukin-2 and Interferons6Topics
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TNF-α Inhibitors: Adalimumab & Infliximab to Omalizumab & Palivizumab: Allergic & Viral7Topics
Severe Combined Immunodeficiency (SCID) to Chronic Granulomatous Disease
Content August 26, 2025
Immunodeficiencies (continued)
B- and T-cell disorders
| DISEASE | DEFECT | PRESENTATION | FINDINGS |
|---|---|---|---|
| Severe combined immunodeficiency | Several types including defective IL-2R gamma chain (most common, X-linked recessive); adenosine deaminase deficiency (autosomal recessive); RAG mutation → VDJ recombination defect | Failure to thrive, chronic diarrhea, thrush Recurrent viral, bacterial, fungal, and protozoal infections |
↑ T-cell receptor excision circles (TRECs) Part of newborn screening for SCID Absence of thymic shadow (CXR), germinal centers (lymph node biopsy), and T cells (flow cytometry) |
| Ataxia-telangiectasia | Defects in ATM gene → failure to detect DNA damage → failure to halt progression of cell cycle → mutations accumulate, autosomal recessive | Triad: cerebellar defects (Ataxia), spider Angiomas (telangiectasia), IgA deficiency ↑↑ sensitivity to radiation (limit x-ray exposure) |
↑ AFP ↓ IgA, IgG, and IgE Lymphopenia, cerebellar atrophy ↑ risk of lymphoma and leukemia |
#boundingbox
| Hyper-IgM syndrome | Most commonly due to defective CD40L on TH cells → class switching defect; X-linked recessive | Severe pyogenic infections early in life; opportunistic infection with Pneumocystis, Cryptosporidium, CMV | Normal or ↑ IgM ↓ IgG, IgA, IgE Failure to make germinal centers |
| Wiskott-Aldrich syndrome | Mutation in WAS gene; leukocytes and platelets unable to reorganize actin cytoskeleton → defective antigen presentation; X-linked recessive | WATER: Wiskott-Aldrich: Thrombocytopenia, Eczema, Recurrent (pyogenic) infections ↑ risk of autoimmune disease and malignancy |
↓ to normal IgG, IgM ↑ IgE, IgA Fewer and smaller platelets |
Phagocyte dysfunction
| Leukocyte adhesion deficiency (type 1) | Defect in LFA-1 integrin (CD18) protein on phagocytes; impaired migration and chemotaxis; autosomal recessive | Late separation (>30 days) of umbilical cord, absent pus, dysfunctional neutrophils → recurrent skin and mucosal bacterial infections |
↑ neutrophils in blood Absence of neutrophils at infection sites → impaired wound healing |
| Chédiak-Higashi syndrome | Defect in lysosomal trafficking regulator gene (LYST) Microtubule dysfunction in phagosome-lysosome fusion, autosomal recessive |
PLAIN: Progressive neurodegeneration, Lymphohistiocytosis, Albinism (partial), recurrent pyogenic infections, peripheral Neuropathy | Giant granules in granulocytes and platelets Pancytopenia Mild coagulation defects |
#boundingbox
| Chronic granulomatous disease | Defect of NADPH oxidase → ↓ reactive oxygen species (eg, superoxide) and ↓ respiratory burst in neutrophils; X-linked form most common | ↑ susceptibility to catalase ⊕ organisms Recurrent infections and granulomas |
Abnormal dihydrorhodamine (flow cytometry) test (↓ green fluorescence) Nitroblue tetrazolium dye reduction test (obsolete) fails to turn blue |
Topics Covered:
- Severe Combined Immunodeficiency (SCID)
- Ataxia-telangiectasia
- Hyper-IgM Syndrome
- Wiskott-Aldrich Syndrome
- Leukocyte Adhesion Deficiency (Type 1)
- Chédiak-Higashi Syndrome
- Chronic Granulomatous Disease
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