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Flashcards in Pathology of TB Deck (10):
1

What causes TB?

inhalation of aerosolized Mycobacterium tuberculosis

2

What arises with initial (exogenous) exposure to TB?

primary TB
*after 3 weeks a Th1 response is mounted, producing interleukin, which drives the macrophages to become competent to contain the organism.
*Note only 5-10% of these people develop clinically significant disease.

3

What does PRIMARY TB result in?

focal, caseating necrosis in the lower lobe of the lung and hilar lymph nodes that undergoes fibrosis and calcification, forming a Ghon complex (classically sub-pleural).

4

Is PRIMARY TB usually symptomatic?

NO, but after 6-8 weeks it will produce a positive PPD test.

5

What is SECONDARY (endogenous) TB?

- reactivation of Mycobacterium tuberculosis from a Ghon complex, due to AIDS, aging, or TNF-a inhibiting drugs.
- it occurs at the apex of the lung due to the high O2 tension and poor lymphatic drainage here.
- this forms cavitary foci of caseous necrosis and may lead to miliary pulmonary TB or tuberculous bronchopneumonia.

6

What are the clinical features of SECONDARY TB?

- fevers, night sweats, cough with hemoptysis and weight loss (cachexia).

7

How do you diagnose SECONDARY TB?

biopsy reveals caseating granulomas and AFB stain reveals acid-fast bacilli (this property allows the bacteria to retain the stain even after treatment with a mixture of acid and alcohol).

8

What are the high-yield sites of systemic spread of TB?

- meninges (meningitis at the BASE of the brain)
- cervical lymph nodes
- kidneys (sterile pyuria)- MOST COMMON extrapulmonary site.
- adrenals (Addison's disease)
- lumbar vertebrae (Pott's disease)

9

How does Mycobacterium tuberculosis prevent phagosome-lysosomal fusion inside the macrophages?

via a protein (CORD FACTOR) that inhibits Ca2+ signals

10

** What are 2 similar bacteria that mimic TB?

Mycobacterium avium and intracellulare