TB Flashcards
What is tuberculosis?
Infectious disease of respiratory tract
How does mycobacterium tuberculosis spread?
Airborne
Describe the pathogenesis of TB (5)
- Alveolar macrophages ingest bacilli. Bacilli multiply in several macrophages.
- Neutrophil chemoattractants and cytokines released.
- Results in inflammatory cell infiltrate reaching lung and draining hilar lymph nodes.
- Macrophages present antigen to T lymphocytes, development of cellular immune response
- Delayed hypersensitivity reaction occurs: result os tissue necrosis and granuloma.
What are the general clinical features of TB? (3)
- Weight loss
- Malaise
- Night sweats
What are the Respiratory clinical features of TB? (4)
- Cough
- Heamoptysis
- Breathlessness
- Upper respiratory zone crackles
Subacute disease of gradual onset
What are some other specific clinical features that you might see? (5)
- Meningeal- headache, drowsy
- GI- pain, periotonitis
- Lymphadenopathy
- Spinal- paraplegia, pain
- Renal- failure
Why is the Ziehl-Neeson test useful for TB?
Detects mycobacterium (shows up as pink stain in blue area)
What other microbiology test can be used? why is it especially useful?
PCR. Can not only confirm TB but also show if its resistant to Rifampicin
What are the distinctive histological features of TB? (2)
- Mutlinucleate giant cell granulomas
2. Caseating (cheesy) Necrosis
What are the key radiological features of TB?
- Upper lobe dominance
- Cavity formation
- Tissue destruction
- Scarring & shrinkage
- Calcification
What is miliary TB?
Heamatogenous spread of bacilli to multiple sites.
What does Miliary TB look like on CXR?
Little nodular infiltrates throughout the lungs
What is the initial therapy for TB?
- Rifampicin
- Isoniazid
- Pyrazinamide
- Ethambutol
All 4 drugs for two months?
What is the continual therapy for TB after the 1st two months?
- Rifampicin
2. Isoniazid
What is the main side effect of Rifampicin?
Colours urine and all body fluids orange. Liver dysfunction
What is the main side effect of ethambutol?
Optic neuritis. Liver dysfunction
What happens in reactivation latent TB?
Do not develop TB during initial exposure, get it later on
What are the features of latent TB?
Symptom free
Culture -
What other infection is closely related to TB?
HIV
What is a Ghon focus on a CXR?
Lung shadow + hilar lymphadenopathy
What are 3 things important for Ghon focus?
- Caseous Granuloma
- lymphadenitis
- Lymphadenopathy
What are some tests for identifying past TB exposure?
- Interferon gamma release assay- Blood sample tests for Mycobacterium antigen
- Mantoux (skin test)- protein Tuberculin used to detect TB. cannot distinguish different types
Why is BCG vaccination helpful?
BCG- weakened form of MTb
