Tuberculosis Flashcards
What is tuberculosis?
An infectious disease usually caused by Mycobacterium Tuberculosis
Where does TB affect?
Generally affects lungs, but can also affect other parts of the body
How is M. TB spread from person to person?
Droplet infection
What happens to M. TB once inhaled?
Some bacilli remain at the site of entry, and the rest are carried to regional lymph nodes
What happens to the bacilli at the site of entry and regional lymph nodes in TB?
The bacilli multiply at both sites, with both sites collectively being referred to as the primary focus
What can happen after bacilli have divided at the primary focus in TB?
They can spread via the blood and lymphatics
What are the risk factors for TB?
- Close proximity to others infected
- Underlying immunodeficiency
- Living in endemic areas
What % of infants with TB have minimal or no symptoms?
Nearly half
What % of children with TB have minimal or no symptoms?
90%
Why do a lot of infants/children with TB have no symptoms or signs of infection?
Because a local inflammatory reaction limits the progression of the infection
What happens if the local host response fails to contain the inhaled TB?
The immune system will respond to the infection 3-6 weeks later
What symptoms occur 3-6 weeks after infection with TB if the immune system cannot contain the inhaled TB?
- Fever
- Anorexia and weight loss
- Cough
What additional problems may arise due to the inflammatory reaction in TB?
May cause bronchial obstruction with collapse and consolidation of the affected lung, and plural effusions
What kind of TB infections can become dormant?
Both symptomatic and asymptomatic
What can happen to latent TB infections?
They can subsequently become reactive and spread by lymphohaematological routes
How might reactivation of TB present?
May present as localised disease, or be widely disseminated to sites such as bones, joints, kidneys, pericardium, and CNS
What investigations can be done in TB?
- TB skin test
- CXR
- Sputum testing
- Interferon-gamma release assays
What are the differential diagnoses of TB?
- Necrotising pneumonia
- Histoplasmosis
- Sarcoidosis
What is involved in the management of pulmonary TB?
2 months of isoniazid, rifampicin, ethambutol, and pyrazinamide, and then 4 months of isoniazid and rifampicin
What is involved in the management of miliary spread of TB?
3 months of isoniazid, rifampicin, ethambutol, and pyrazinamide, then 12-18 months of isoniazid and rifampicin
What needs to be done once TB is diagnosed?
It is a notifiable disease, and contract tracing is required
Why is contact tracing required in TB?
So those exposed to the patient can undergo tuberculin testing and CXR screening
