Tuberculosis (TB) Flashcards
What pathogen causes it?
Mycobacterium tuberculosis
Also called M.bovis
How is it transmitted?
Where does it tend to spread more?
Via air droplets in the air - just like COVID
Overcrowding
Prisons
Pathophysiology - Primary infection:
Primary infection:
- What are tubercles?
- These tubercles can become caseating. What does this mean?
- Where does the infection usually spread to?
Pathophysiology - Latent TB:
- Not everyone has an active infection. How would you know someone has latent (asymptomatic) TB?
- What percentage of people have a reactivation with latent TB?
- What causes a reactivation?
Tubercles are nodules that contain caseous necrosis, which forms in the lungs as a result of an infection with Mycobacterium tuberculosis in the patients with tuberculosis. Granulomas form in the infected tissue and undergo necrosis in the centre. Tubercles are also known as tuberculous nodules, or tuberculomas.
Lymph nodes
Latent TB is where you’ve been infected with the TB bacteria, but do not have any symptoms of active infection.
They have a positive skin/blood test.
The immune system deals with it by forming granulomas preventing bacteria growth and spread
5-10 %
Immunosuppression
Physical stress
Clinical features:
Are the symptoms chronic or acute?
What type on onset does it have?
What systemic S+S do they have? - 5
Pulmonary TB:
- What type of cough do they have?
- What other features may have have wit the cough?
- What 4 other lung diseases may they progress to having?
CHRONIC - THIS IS NOT A NEW INFECTION - IT HAS AN INSIDIOUS ONSET
Low-grade fever Anorexia Weight loss Malaise Night sweats
Dry then productive
Haemoptysis
Pleurisy
Pneumonia
Pleural effusion
Lobar collapse
Bronchiectasis
Clinical features:
Tuberculous lymphadenitis:
- What is it?
- Is it painful?
- Where does it happen?
GI TB:
- Where does most disease happen?
- What GI symptoms do they have?
- Why is bowel obstruction common?
Painless enlargement of cervical or supraclavicular lymph nodes
Ileocaecel region
Abdo pain
Vomiting
The most common complication of abdominal tuberculosis is obstruction due to NARROWING of the lumen by hyperplastic caecal tuberculosis, by strictures of the small intestine or by inflammatory adhesions.
Clinical features:
Spinal TB:
- They have pain and tenderness in the spine. How long does this happen for?
- When may patients actually present?
- What may it lead to?
- This whole clinical picture is called ____ disease. Fill the gap?
Genitourinary TB:
- What sort of symptoms do they have?
- Why is it important to know about?
Cardiac TB:
- What cardiac pathology does it cause via inflammation?
Weeks to months - slow insidious progression
When deformity neurological symptoms develop
Bony destruction
Vertebral collapse
Soft tissue abscess
Pott's disease ---------- Chronic, intermittent or silent!! - Dysuria - Loin/back pain - Haematuria
It is the second most common TB presentation in the UK.
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Pericarditis
Clinical features:
CNS TB:
- How does it spread?
- What does it form in the brain?
- What neurological symptoms do they have?
Skin TB:
- It forms something called lupus vulgaris. What is it?
- What colour are the nodules?
- How do they feel?
- Where do they tend to appear? - 2
- They also get erythema nodosum. What is it?
The blood
Tuberculomas
Neurological deficit Confusion Seizures Headache Meningism ==== Peristent progressive cutantous TB
Red-brown
Rough
Face and shin
Erythema nodosum is a type of panniculitis, an inflammatory disorder affecting subcutaneous fat. It presents as tender red nodules on the anterior shins.
Clinical features:
Military TB - SEVERE MANIFESTATION:
- Why is it called military?
- What does it look like on XR?
- How does it spread to the rest of the body?
Because it is due to the formation of discrete foci (2mm) of granulomatous tissue throughout the lung
Dissemination throughout the body including meningeal involvement.
The blood - haematogenous
Risk factors:
What continents are at risk of TB?
Knowing TB is spread by air droplets, what may increase someone risk?
Africa
South Asia
Being homeless
Living in cramped housing
Contact with infected individuals
Investigations - Latent TB - Screening:
Who should TB tests be offered to?
Tuberculin skin testing (TST):
- What is another name for it?
- How is it done?
- How do you know you have a positive test?
Interferon-gamma release assays (IGRAS):
- How does this test for TB?
- This test is more specific than above!
What is a limitation of the above tests?
There will be an induration (bump) around the site
Close contacts
Immunocompromised
Health workers
High-risk populations
Mantoux test
Tuberculin is injected into the dermal layer of the skin
It measures interferon-gamma which is released from T-cells reacting to TB antigens
They can’t distinguish between active and latent TB.
Investigations - Active TB:
CXR - Primary Infection:
- What do you see?
- Where does it usually happen?
- What is a Ghon focus and where does it typically happen?
- What extra-parenchymal features may you see?
- These features may resolve following a successful immune response. What will they leave?
CXR - Secondary Infection:
- They may have air-filled spaces in the apices. What type of lesion is this called?
CXR - Military TB:
- What do you see throughout the lung fields?
- Why is it called military?
Calcified nodes
Fibronodular/linear opacities in the upper lobe
A Ghon focus is a primary lesion usually subpleural, often in the mid to lower zones, caused by Mycobacterium bacilli (tuberculosis) developed in the lung of a nonimmune host (usually a child).
Ipsilateral hilar lymphadenopathy
Effusion
Cavitating lesions
—
Diffuse shadows throughout lung fields
Due to there being more nodules which can’t easily be counted t
Investigations - Active TB:
Getting samples:
- How many sputum samples are needed?
- What time of the day does a 1 of them have to come from?
- What fluid can be nebulised to induce sputum production?
- What can be done in children?
Extrapulmonary - What else can be aspirated or biopsied?
3
Early morning - the rest can be spontaneous
Nebulised saline
Bronchoalbeolar lavage of gastric lavage
Lymph nodes Ascites Organs Pus Urine CSF
Investigations - Active TB:
Sputum smear:
- AFB smear is done to it. What does this stand for?
- Why is this used?
- This is not that sensitive. What can be done which is more sensitive?
NAAT:
- What does this stand for?
- How does it work?
- Why is it used?
Acid-fast bacilli (AFB)
Doesn’t come up on normal staining
Culture - used to assess drug sensitivity
Nucleic acid amplification test
Detects DNA of M.tuberculosis in sputum by DNA or RNA amplification
It allows for rapid diagnosis before culture
Can also detect drug sensitivity
Investigations - Both:
What chronic infection is screened for which could be a possible cause?
Basic bloods that should be done to assess the baseline before starting Rx- 3
FBC
LFT
U&E
Management - Active TB:
Who Rx them?
Infection control:
- Who should be notified?
- Who needs to be screened?
- Where does the patient need to be put in?
Drug Rx:
- Should Rx be started before or after culture?
- How long are they given drugs for?
Mneumonic for drugs - RIPE - what does it stand for?
Quarantined in a single room for the first 2 wks of Rx
A specialist TB clinician
Public health authorities
Close contacts
Before if clinical suspicion is high
6 months in total
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
