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Pathology II — Inflammation & Repair — USMLE Step 2 CK Notes
Free, high-yield revision notes for USMLE Step 2 CK. Read here, or drill the same material as questions and flashcards in the app.
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Acute inflammation
- Cardinal signs: rubor, calor, dolor, tumor, functio laesa
- Vascular phase: transient vasoconstriction then vasodilation and increased permeability (histamine, leukotrienes)
- Cellular phase — leukocyte extravasation in order: margination → rolling (selectins) → adhesion (integrins–ICAM-1) → transmigration (PECAM-1) → chemotaxis
- Neutrophil chemoattractants: C5a, LTB4, IL-8, bacterial products
Key cell-defect diseases (map the step to the disease)
- Leukocyte adhesion deficiency 1 (CD18 integrin): no pus, delayed cord separation, neutrophilia
- Chédiak-Higashi (LYST, defective phagosome-lysosome fusion): giant granules, albinism, recurrent infection
- Chronic granulomatous disease (NADPH oxidase): catalase-positive infections, abnormal dihydrorhodamine test
Chemical mediators worth memorising
- Vasodilation: prostaglandins, nitric oxide, histamine
- Pain: bradykinin, PGE2
- Fever: IL-1, IL-6, TNF, PGE2
- Acute-phase reactants (from IL-6): CRP, fibrinogen, hepcidin, ferritin, serum amyloid A
- Negative acute-phase reactant: albumin, transferrin
Chronic inflammation and granulomas
- Cells: lymphocytes, plasma cells, macrophages
- Granuloma: epithelioid macrophages ± giant cells; driven by Th1 and interferon-gamma; TNF maintains it (anti-TNF drugs reactivate TB)
- Caseating (TB, fungi) vs non-caseating (sarcoid, Crohn, berylliosis, cat-scratch, foreign body)
Repair
- Labile (gut, skin, marrow), stable (liver, proximal tubule), permanent (neuron, cardiac, skeletal muscle)
- Granulation tissue = new capillaries + fibroblasts + loose matrix (NOT the same as a granuloma)
- VEGF → angiogenesis; TGF-beta and FGF → fibrosis; excess TGF-beta → keloid
- Vitamin C and zinc needed for collagen cross-linking and wound healing
AI-authored Step 1 pathology · not editorially reviewed · study aid only.
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