TB Flashcards
Ix of TB
Mantoux: more sensitive for active diseaseTB (quantaferon) gold: - less sensitive in acute disease- +ve if BCG vaccineCXRZeil Neelson stain
What is primary TB?
Occurs following first exposure to the organism- Usually self limited and characterised by an area of necrotizing granulomatous inflammation (Ghon focus) in the lung and in draining LN (Ghon’s complex)
What is a Ghon’s focus
Loated in lower portion of R upper lobe or upper portion of RLL (just above or below the interlobar fissure)
What is a Ghon’s complex
Combination of peripheral lung and LN lesions in primary TB
What is progressive TB?
Progression of primary to spreading elsewhereOccurs in less than 10% of pts, where most have underlying immune compromise
Consequences of progressive TB?
Cavitary fibrocaseous TBMiliary TBTuberculous bronchopneumonia
What is miliary TB?
TB sepsisHaematogenous dissemination may give rise to miliary TB, confined only to the lungs or involving other organs
Favoured sites of miliary TB?
Bone marrowLiverSpleenKidney LN
What is tuberculous bronchopneumonia
If TB infection spreads throughout the lung
What is secondary TB?
Due to reactivation of a dormant focus of primary infection or reinfection
What are the two factors that promote reactivation of healed primary lesions?
CorticosteroidsHIV infection
Location of secondary TB in lungs?
Typically located in the apex of the upper lobe of 1 or both lungs - high O2 tension favours growth
Histopathology of granuloma
Epitheliod histiocytes, lymphocytes, Langhan’s giant cell (when epithelioid cells join)
DDx of TB (other granulomatous inflammation in lungs)
Infections: mycobacteria, fungi, parasitesNon infectious causes: sarcoidosis, pneumonitis, Wegener granulomatosis, Churg-Straus syndrome, aspiration pneumonia, rhematoid nodules, bronchocentric granulomatosis
