USMLE-First Aid : Adaptations, Inflammation and Neoplasm Flashcards
Cellular Adaptations
Reversible changes that can be physiologic or pathologic. If stress is excessive or persistent, adaptations can progress to cell injury.
Hypertrophy
↑ structural proteins and organelles → ↑ in size of cells. Example: cardiac hypertrophy.
Hyperplasia
Controlled proliferation of stem cells and differentiated cells→ ↑ in number of cells.
Atrophy
↓ in tissue mass due to ↓ in size and/or number of cells (apoptosis).
Metaplasia
Reprogramming of stem cells → replacement of one cell type by another that can adapt to a new stress. Usually due to exposure to an irritant.
Dysplasia
Disordered, precancerous epithelial cell growth; not considered a true adaptive response. Characterized by loss of uniformity of cell size and shape (pleomorphism); loss of tissue orientation; nuclear changes
Coagulative Necrosis - Seen in :
Ischemia/infarcts in most tissues (except brain)
Coagulative Necrosis - Due to:
Ischemia or infarction; injury denatures enzymes → proteolysis blocked
Coagulative Necrosis - Histology:
Preserved cellular architecture (cell outlines seen), but nuclei disappear; ↑ cytoplasmic binding of eosin stain
Liquefactive Necrosis - Seen in :
Bacterial abscesses, brain infarcts
Liquefactive Necrosis - Due to:
Neutrophils/Microglia release lysosomal enzymes that
digest the tissue
Liquefactive Necrosis - Histology:
Early: cellular debris and macrophages
Late: cystic spaces and cavitation (brain)
Neutrophils and cell debris seen with
bacterial infection
Caseous Necrosis - Seen in :
TB, systemic fungi
Caseous Necrosis - Due to:
Macrophages wall off the infecting microorganism → granular debris
Caseous Necrosis - Histology:
Fragmented cells and debris surrounded
by lymphocytes and macrophages (granuloma)
Fat Necrosis - Seen in :
Enzymatic: acute pancreatitis (saponification of
peripancreatic fat)
Nonenzymatic: traumatic (eg, injury to breast tissue)
Fat Necrosis - Due to:
Damaged pancreatic cells release lipase,
which breaks down triglycerides; liberated fatty acids bind calcium → saponification (chalky white appearance)
Fat Necrosis - Histology:
Outlines of dead fat cells without peripheral nuclei; saponification of fat (combined with Ca2+) appears dark blue on H&E stain
Fibrinoid Necrosis - Seen in :
Immune vascular reactions (eg, Polyarteritis Nodosa)
Nonimmune vascular reactions
(eg, hypertensive emergency-Renal vessels, preeclampsia-Placenta)
Fibrinoid Necrosis - Due to:
Immune complex deposition (type III
hypersensitivity reaction) and/or plasma protein
(eg, fibrin) leakage from damaged vessel
Fibrinoid Necrosis - Histology:
Vessel walls are thick and pink
Gangrenous Necrosis - Seen in :
Distal extremity and GI tract, after chronic ischemia
Gangrenous Necrosis - Due to:
Dry: ischemia
Wet: superinfection
Gangrenous Necrosis - Histology:
Dry- Coagulative
Wet - Liquefactive superimposed on coagulative
Ischemia - Most Prone Regions: Heart
Subendocardium (LV)
Ischemia -Most Prone Regions: Brain - Watershed areas
Watershed areas (border zones) receive blood supply from most distal branches of 2 arteries with limited collateral vascularity. (From ACA,MCA,PCA) (This is also relevant for GI)
Ischemia -Most Prone Regions: Brain - Neurons most vulnerables
Purkinje cells of the cerebellum and pyramidal cells of the hippocampus and neocortex (zones 3, 5, 6).
Ischemia -Most Prone Regions: Kidney
Straight segment of proximal tubule (PT-medulla)
Thick ascending limb (TAL-medulla)
Ischemia -Most Prone Regions: Liver
Area around central vein (zone III)
Ischemia -Most Prone Regions: Colon
Splenic flexure (Griffith point),a rectosigmoid junction (Sudeck point)
Red infarct
Occurs in venous occlusion and tissues with
multiple blood supplies (eg, liver, lung , intestine, testes), and with reperfusion (eg, after angioplasty). Reperfusion injury is due to damage by free radicals.
Pale infarct
Occurs in solid organs with a single (endarterial) blood supply (eg, heart, kidney)
Systemic Amyloidosis:
Primary amyloidosis - Fibril and When is it seen?
AL (from Ig Light chains). Seen in Plasma cell disorders
eg, multiple myeloma
Systemic Amyloidosis:
Secondary amyloidosis - Fibril and When is it seen?
Serum Amyloid A (AA). Seen in chronic inflammatory
conditions, (eg, rheumatoid arthritis, IBD, familial
Mediterranean fever, protracted infection)
Systemic Amyloidosis:
Dialysis-related amyloidosis- Fibril and When is it seen?
β2-microglobulin. ESRD and long term dialysis
Localized Amyloidosis:
Alzheimer disease - Fibril
β-amyloid protein
Localized Amyloidosis:
Type 2 diabetes mellitus - Fibril
Islet amyloid polypeptide
IAPP
Localized Amyloidosis:
Medullary thyroid cancer - Fibril
Calcitonin
Localized Amyloidosis:
Isolated atrial amyloidosis - Fibril
ANP
Localized Amyloidosis: Systemic senile (age related) amyloidosis
Normal (wild-type) transthyretin (TTR)
Familial amyloid cardiomyopathy or polyneuropathies - Fibril
Mutated transthyretin (ATTR)
Detection of Amyloidosis
Congo red stain, apple-green birefringence
Common systemic menifestations of Amyloidosis
Restrictive cardiomyopathy, Macroglossia, Nephrotic
syndrome, carpal tunnel syndrome and Neuropathy
Rubor (redness), calor (warmth) - Mechanism:
Vasodilation by Histamine, prostaglandins, bradykinin, NO
Tumor (swelling-Inflammatory cardinal sign) - Mechanism:
Endothelial contraction and Vascular Permeability: leukotrienes (C4, D4, E4), histamine, serotonin
Dolor (pain) - Mechanism:
Sensitization of sensory nerve endings - Bradykinin, PGE2, histamine
Ferritin - Is it a Positive or Negative Acute Phase Reactant?
Positive Acute Phase Reactant - More FFiSH in the C
Ferritin - Binds and sequesters iron to inhibit microbial iron scavenging.
Fibrinogen - Is it a Positive or Negative Acute Phase Reactant?
Positive Acute Phase Reactant - More FFiSH in the C
Fibrinogen - Coagulation factor; promotes endothelial repair; correlates with ESR.
Serum amyloid A - Is it a Positive or Negative Acute Phase Reactant?
Positive Acute Phase Reactant - More FFiSH in the C
Serum amyloid A - Prolonged elevation can lead to amyloidosis.
Hepcidin - Is it a Positive or Negative Acute Phase Reactant?
Positive Acute Phase Reactant - More FFiSH in the C
Hepcidin - ↓ iron absorption (by degrading ferroportin) and ↓ iron release (from macrophages) → anemia of
chronic disease.
CRP - Is it a Positive or Negative Acute Phase Reactant?
Positive Acute Phase Reactant - More FFiSH in the C
CRP - Opsonin; fixes complement and facilitates phagocytosis. Measured clinically as a nonspecific sign of ongoing inflammation.
Albumin - Is it a Positive or Negative Acute Phase Reactant?
Negative Acute Phase Reactant
Albumin - Reduction conserves amino acids for positive reactants.
Transferrin - Is it a Positive or Negative Acute Phase Reactant?
Negative Acute Phase Reactant
Transferrin - Internalized by macrophages to sequester iron.
When is ESR elevated?
Most anemias, Infections, Inflammation, Cancer, Renal disease and Pregnancy
When is ESR lowered?
Sickle cell anemia, Polycythemia, HF, Microcytosis
and Hypofibrinogenemia
When is Procalcitonin elevated?
Infections - especially of bacterial origin
Wound healing - Tissue mediators:
FGF - Role
Stimulates angiogenesis
Wound healing - Tissue mediators:
TGF-β - Role
Angiogenesis, fibrosis
Wound healing - Tissue mediators:
VEGF - Role
Stimulates angiogenesis
Wound healing - Tissue mediators:
PDGF - Role
Remodeling and smooth muscle cell migration.
Stimulates fibroblast growth for collagen synthesis.
Wound healing - Tissue mediators:
Metalloproteinases - Role
Tissue remodeling
Wound healing - Tissue mediators:
EGF - Role
Stimulates cell growth via tyrosine kinases
Bacterial causes of Granuloma:
Mycobacterium Tuberculosis, Mycobacterium Leprae, Bartonella Henselae, Listeria monocytogenes, Treponema pallidum.
Fungal causes of Granuloma:
Endemic mycoses (eg; Histoplasmosis)
Protozoa causes of Granuloma:
Schistosomiasis
Immune-mediated (Non-Vascular) Etiologies for Granuloma:
Sarcoidosis, Crohn’s disease, PBC , subacute Thyroiditis
Vasculitis - Etiologies for Granuloma:
Wegener’s Granulomatosis, Churg-Strauss, Giant cell arteritis, Takayasu arteritis
Foreign bodies - Etiologies for Granuloma:
Berylliosis, Talcosis, Hypersensitivity pneumonitis
Hereditary Etiology for Granuloma:
Chronic Granulomatous disease