Tuberculosis Flashcards
What is tuberculosis (TB)?
A bacterial infection characterized by the growth of nodules (tubercles) in the tissues, esp the lungs.
What is the cause & pathophysiology of TB?
- Mycobacterium tuberculosis is inhaled
- Small, aerobic, nonmotile, bacillus
- Divides 16/20hrs
- Causes local inflammatory responce
-
Granuloma forms (Macrophages (& may fuse to form Langhans giant cell) surround the foreign agent (caseous necrosis)
- This is all surrounded by Fibroblasts
- Spread to lymph nodes (LN & granuloma = Gohn complex)
- 5% → Local progression/ dissemination
- 90% end here → dormant
- 5% → Latent reactivation!
- x70 chance in immunosuppression; HIV, post-transplant, chemotherapy for cancer, IV drug users
- x3 chance in malnourished, DM, smoking
- New exposure to TB
- 5% → Latent reactivation!
Draw a granuloma
What are the clinical features of pulmonary TB?
Main manifestaton!
- Silent
- Malaise, weight loss, night sweats
- 3Cough, sputum, haemoptysis
- 3Pleuritic chest pain (pleurisy), pleural effusion, pulmonary infection
-
4 C’s
-
CXR;
- Calcification
- Cavitation (aspergilloma/ mycetoma)
- Cicatrization (scars, fibrosis)
- Histology; Caseating granulomata
-
CXR;
What is miliary TB?
What may its clinical features be?
Following haematogenous dissemination (spread) to multiple organs (tiny spots known as milits).
Signs may be;
- CXR; reticulonodular shadowing
- Retinal TB
- Granuloma in various organs
What are the clinical features of genitourinary TB?
UTI symptoms..
- Inc frequency, dysuria
- Loin/ back pain
- Haematuria
- Sterile pyuria (inc WCC in uria but urine is sterile)
What are the clinical features of bone TB?
Pott’s vertebra (TB in vertebra);
- Vertebral collapse;
- 2 vertebra either side of a vertebral disc, disc becomes avascular
- Disc tissue dies and is broken down by caseation
- Causing narrowing & collapse
What are the clinical features of skin TB?
Lupus vulgaris.
- Jelly-like nodules on face/ neck
- Painful
What are the clinical features of peritoneal TB?
- Abdo pain & GI upset
- AFB in ascites (acid-fast bacilli)
What are the clinical features of acute TB pericarditis?
Primary exudative allergic lesion?
May lead to chronic pericardial effusion & pericarditis
What are the clinical features of chronic pericardial effusion & constrictive pericarditis?
Fribrosis/ calcification may be prominent with spread to myocardium.
What are the clinical features of TB meningitis?
Prodrome;
- Fever, headache, vomiting, drowsiness, meningism, delirium
- +/- seizures
- CNS signs; tremor, papilloedema, cranial nerve palsies
What are the findings of classical TB?
4C’s!
- Histology; Caseating granulomata
- CXR; **Calcification,Cavitation, Cicatrization **(scars, fibrosis)
How would you diagnose latent TB?
Latent TB has no symptoms.
- Mantoux test (inject tuberculin, measure diameter of induration responce)
- IFN-gamma testing (eg Quantiferon TB Goldor T-spot TB)
How would you diagnose Active TB?
- CXR
- Calcification (patchy/ nodular shadows)
- Cavitation
- Cicatrization (scars, fibrosis)
- Loss of volume
- Miliary reticulonodular shadows - miliary TB
- Sputum samples (minimum 3)
- Microscopy, culture & sensitivity testing
- Acid-fast bacilli
