TB Revision Flashcards
Organs that TB can affect
Any organ in the body, particularly the lungs
Stain used to view TB under a microscope
Ziehl-Neeson stain
Shape of TB
Bacillus
ZN
Stain with carbol-fuschin, decolourise with acid.
Typical pathological features of body’s reaction to TB
Granulomas
Caseous necrosis
Primary TB 1 2 3 4 5
In those not previously exposed.
Mild, self-limiting illness, or subclinical.
Peripheral area of granulomatous inflammation and caseation in the lung periphery(Ghon focus)
Drainage of bacteria to hilar lymph nodes, which also caseate
Ghon complex = Ghon focus + caseated lymph node
Most common outcomes of primary TB
Immune response clears the infection.
Ghon complex heals by fibrosis, often with scarring.
Secondary TB emergence
Occurs in those previously infected with TB (immune response is sensitised), OR:
Re-emergence of dormant TB infection (with immunosuppression).
Which part of lungs does secondary TB infect?
Apical areas of upper lobes
Characteristic feature of secondary TB
Cavitation of caseous necrosis (erosion of bronchial wall by caseous necrosis).
Dystrophic calcification
Complications of secondary TB 1 2 3 4 5
Progressive spread of caseation into surrounding lung
Erosion of blood vessels (leads to haemoptysis)
Erosion into bronchial tree leading to cavitation and spread of infection via airways.
Pleural inflammation and fibrosis
Lung scarring.
Miliary TB
Numerous small granulomas in lungs and other organs.
Can see gross white dots (granulomas)
Size of granulomas in miliary TB
About the size of Millet seeds (~2-3mm)
How is miliary TB caused?
Dissemination of TB via blood vessels.
When is miliary TB More common?
Secondary TB
