Tuberculosis Flashcards
Define tuberculosis.
Tuberculosis (TB) is a chronic granulomatous disease. In humans it is caused by Mycobacterium tuberculosis.
It is a notifiable disease.
Describe the epidemiology of tuberculosis.
TB is the second most common cause of death from infectious diseases after HIV/AIDS.
The prevalence in England is much higher in large urban areas, with 40% of cases being reported in London.
Only 30% become infected and of those 10% progress to active TB and 90% to latent TB.
What causes TB? Describe the pathophysiology.
Transmitted by inhalation of aerosolised droplets containing the bacterium
Inhalation of droplet nuclei → deposition in alveoli → engulfment by alveolar macrophages → eventually kills the macrophage → release into surrounding area.
Containment mainly depends on Th1 and macrophages response → granuloma with a centre that contain necrotic material (caseous centre) → granulomas (tubercles) serve to prevent spread of TB.
Latent individuals are non-infectious and are tuberculin skin test-positive.
What are the risk factors for TB?
- Alcohol use
- HIV
- Homelessness
Other:
- exposure
- birth in an endemic country
- HIV infection - high risk of reactivation
- immunosuppressants- esp systemic corticosteroids and TNF-alpha antagonists
- silicosis (x30 risk)
- apical fibrosis
- malignancy
- ESRD -patients on haemodialysis
- intravenous drug use
- malnutrition
- alcoholism
- diabetes
- high-risk congregate settings - correctional facilities, homeless shelters, or nursing homes
- low socio-economic status or black/Hispanic/Native American ancestry
- age
- tobacco smoking
What are the main 4 presenting features of TB?
Cough
Fever
Sweats
Weight loss - should quantify this
What investigations would you do for suspected TB?
Bloods
- FBC - WCC usually normal in TB, no neutrophilia, low lymphocytes in HIV, anaemia of chronic disease
- LFT - check liver function before giving TB drugs
- U&Es - when adjusting drug doses
- HIV/HBV/HCV tests - same epidemiology as TB
- HbA1c
Microbiological:
- Sputum acid-fast bacilli (AFB) - Ziehl Neelsen stained smear
- Sputum culture “for TB” - must say that it is for TB when sending, GOLD standard for diagnosis. Sensitivities can be tested too.
- PCR/nucleic acid amplification tests (NAAT) - finds rifampicin probe for resistance (>90% likely to have ISO resistance too)
Latent tests:
- Mantoux
- IGRA
What would a CXR of TB show?
Typical - fibronodular opacities in the upper lobes with or without cavitation
Atypical - opacitis in the middle or lower lobes, hilar or paratracheal lymphadenopathy and/or pleural effusion.
- Normal chest radiograph
- Bilateral ill defined upper lobe infiltrates/consolidation
- Bilateral hilar lymphadenopathy
- Cardiomegaly
- Right upper lobe collapse
What is shown on the radiograph?
His chest radiograph shows bilateral ill defined upper lobe infiltrates/consolidation.
Which is consistent with tuberculosis (active infection)
How is tuberculosis treated?
(latent TB in non-pregnant and HIV negative) - Isoniazid and pyridoxine
(active TB in non-pregnant and HIV negative) - initial phase therapy: isoniazid+pyridoxine+rifampicin + pyrazinamide+ ethamutol. continuation phase therapy: isionazid+ pyridoxine + rifampicin .
What are the three outcomes of infection with TB?
- clearance of TB
- persistent latent infection
- progression of primary disease
What are the three outcomes of infection with TB?
- clearance of TB
- persistent latent infection
- progression of primary disease
What parts of the body does TB affect?
ANY SITE
- Lungs/lymph nodes- Ghon focus with lymph nodes is called a Ghon complex
- Neck - usually sits latent in lymph nodes in neck
- Brain - tuberculoma, CNS meningitis
- Eyes - uveitis with granulomas
- Larynx - laryngeal TB is very infectious
- Pericardial TB
- Pleura - without lung involvement
- Blood stream - miliary TB (still considered a pulmonary type of TB)
- Abdominal - often misdiagnosed
- Genitourinary - tubulointerstitial nephritis, fibrosis of fallopian tubes
- Bones - joints, long bones
- Spine - Pott’s disease, may cause paralysis in severe cases
- Skin - lupus vulgaris, erythema nodosum
What is abdominal TB misdiagnosed as?
Crohn’s - because both have granulomatous histology
What are some differentials for erythema nodosum?
AI - sarcoid and IBD
Infection - TB, streptococcal
Drug - COCP
Idiopathic
What is the pharmacology of rifampicin?
p450 inhibitor
So COCP will be less effective
What is the diagnosis?
Miliary TB
What is the diagnosis?
Previous TB
