Tuberculosis Pathogenesis and Clinical Features Flashcards Preview

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Flashcards in Tuberculosis Pathogenesis and Clinical Features Deck (10):

Mycypobacterium TB


Slow growing

Acid-fast - mycolic acid

Humans are onyl reservoir


Active vs. latent

Active - has sx, CXR evidence and should be able to recover TB bacilli

Latent - immune sx controlled nad asymptomatic...may have G/R complex



TB inhaled...AM engulfs but cannot destroy...form early and small granuloma...then well-formed granuloma with central caseous necrosis - infected macrophjages killed (DTH) resulting in cessation of growth

If good immune sx, then healed granuloma

If not, then liqufactive necrosis occurs and the infection can spread



TST - Most pts control initial infection...get 5% lifetime risk of developing active dz

TST- positive indicates prior exposure and established DTH (5-7 weeks0

IGRA has same implicatiins


Mechs of spread

Erosion into bronchus (endobronchial spread)

Erosion into lymphatic - hematogenous sread (lungs)

Erosion in pulmonary vein (systemic spread)


Patho summary

INtracellular pahtogen that needs CMI for control

DTH is form of CMI manifested by caseous necrosis AND skin test reactivity

If poor, then active disease with negative TST and no DTH or cavity

If intermediate and active, then DTH positive and cavity forms

If latent, then positive DTH and no cavity


Bacillary load

Liaquefactive ncrosis leads to explosive extracellular growth

Higher loads mean more likely to show up in sputum and therefore more infedctvity


Radiography relationship to pathogenesis

Most have intiail infection leaving a nodule with associated adenopathy (middle and lower lobes...primary will also show up in these lobes)

Later, reactiviation may occur in upper areas

Poor CMI could lead to hematogenous dissemination


Ghon/Ranke complexes

Nodule representing the primary lesion of pulmonary TB with associated ipsilateral adenopathy

If both are calcified, then old and inactive dz


Other miliary patterns

Blastomycosis, histoplasmosis, TB