Tuberculosis Flashcards
What is TB?
TB is a granulomatous disease caused by the Mycobacterium tuberculosis complex. TB most commonly affects the lung, but it can affect almost any organ.
How does infection occur?
Infection is through droplet inhalation and therefore commonly spread by coughing and sneezing.
What happens after exposure to TB?
The mycobacterium is engulfed by macrophages in the lung. Most people (70%) clear the infection at this point and have a spontaneous recovery. Those who do not develop primary TB (30%).
Discuss primary TB.
Primary TB infection leads to asymptomatic latent TB in most people. Latent TB can re-activate in 10%, causing post-primary TB.
Discuss the complications of primary TB.
A small number of people with primary TB develop primary progressive pulmonary or extra-pulmonary TB through haematogenous dissemination. Extra-pulmonary TB can affect almost any organ.
Define Miliary TB.
A disseminated form of TB commonly found in lungs, which can develop from primary progressive or post-primary TB. The name originates from millet seeds which are said to resemble the lung nodules occuring in miliary TB.
What are the risk factors associated with TB?
- Close contact with a patient infected with pulmonary TB.
-Demographic features which confer increased risk are ethnic minorities, those born in or travelling from high prevalence areas, extremes of age and homelessness.
-Immunosuppresion e.g., HIV.
What are typical general symptoms of TB?
Fever, lethargy, anorexia, weight loss, night sweats, enlarged and tender lymph nodes.
What are the typical pulmonary symptoms of TB?
Cough (usually chronic), sputum (initially dry, then purulent or blood-stained), breathlessness and pleuritic chest pain.
What would typical clinical findings on a respiratory examination include?
-Sputum pots with purulent or blood stained sputum.
-Enlarged, tender lymph nodes.
-Crackles or bronchial breathing over consolidation.
-Dullness to percussion and decreased fremitus over pleural effusions.
What various appearances can pulmonary TB have on a CXR?
-Patchy or lobar consolidation.
-Miliary TB.
-Cavitating lesions (more common in post-primary).
-Tuberculoma (a caseating granuloma).
-Calcified tuberculoma (Ghon focus) or lymph nodes.
-Lymphadenopathy.
-Pleural effusion.
What is the treatment for TB without CNS involvement?
-Isoniazid, rifampicin, pyrazinamide and ethambutol for two months, follower by…
-Isonazid and rifampicin for a further four months.
Why is pyridoxine (vitamin B6) always given with isonazid?
To avoid peripheral neuropathy.
What are some pulmonary complications of TB?
Pleurisy.
Pleural effusions.
Empyema.
Pneumothorax.
Bronchiectasis.
Respiratory failure.
What are the adverse affects of TB medical treatment?
- Hepatitis: rifampicin, isoniazid and pyrazinamide.
-Visual disturbances: ethambutol.
-Peripheral neuropathy: isoniazid.
-Drug interactions: most notable with anti retroviral therapy used in HIV.
