Tuberculosis Flashcards
If you have what then you are more likely to get TB?
HIV
Where are the TB incidence rates the highest?
Southern africa
Saharan africa
South east asia
Causative organisms of TB
Mycobacterium tuberculosis Mycobacterium bovis (bovine TB) Mycobacterium avium-intracellulare (HIV)
Transmission of mycobacterium tuberculosis
Respiratory droplets - coughing and sneezing
Transmission of mycobacterium bovis
Consumption of infected cows milk - deposited in cervical and intestinal lymph nodes
Pathology of TB
Infected with TB
Mycobacteria spread by lymphatics to draining hilar lymph nodes
Haematogenous seeding of mycobacteria to all organs of the body
Presentation of TB
Usually no symptoms Fever Malaise Erythema nodosum Rarely chest signs Initial lesion + local lymph node Lesion may calcify
Complications of TB
Primary focus continues to enlarge - cavitation
Enlarged hilar lymph compresses bronchi, lobar collapse
Enlarged lymph node discharges into bronchus (TB bronchopneumonia)
In a small number (1%) 6 - 12 months after infection, after the infection…….
Miliary TB fine mottling on X ray, widespread small granulomata
Meningeal TB, severe, CSF high protein, lymphocytes
TB pleural effusion
Possible causes post primary disease of TB
Reactivation of mycobacterium from latent primary infection spread by blood stream around the body
New reinfection from outside source, susceptible previously infected host
What in the body can TB affect?
Pulmonary disease Lymph nodes, usually cervical (scrofuloderma) Renal CNS (tuberculous meningitis) Bone and joint; spine (vertebral bodies - potts disease), hip GI tract GU Infertility Van deferens and fallopian tube effects Constrictive pericarditis, pericarditis Ascites Ileal TB - obstruction Addisions disease Lupus vulgaris
When does post primary disease of TB occur?
1 - 5 years
What is post primary TB?
Reactivation of latent disease
Features of post primary TB
May occur at any age
May be no symptoms for months
Progressive and occur over several months
Presentation of post primary TB
Cough Sputum Haemoptysis Pleuritic pain SOB Malaise + weight loss + night sweats (systemically unwell)
Who should you have a high index of suspicion of TB in?
Immunocompromised (HIV, corticosteroid therapy) Malnutrition Alcoholism Vagrants Previous gastric surgery Malignancy DM Adolescence Elderly Recent immigrants from high prevalent countries
What are the investigations of TB?
3 sputum specimens on successive days
- Sputum smear - Ziehl-Neilsen stain (ZN stain)
- Sputum culture
- Sputum PCR
CXR
- patchy (shadowing, often apices/upper zones or apex of lower lobes), often bilateral
- cavitation if advanced
- may calcify if chronic or healed TB
Further investigations if sputum -ve
- CT thorax
- Bronchoscopy with bronchoalveolar lavage
- pleural aspiration and biopsy if pleural effusion
What is cavitation?
Formation of an empty space
Different treatment regimes for treating TB
A) Rifampicin + Isoniazid + Ethambutol + Pyrazinamide for 2 MONTHS
B) Rifampicin + Isoniazid for 4 MONTHS
S/Es of rifampicin
Orange irn bru urine + tears
Deranged LFTs / Hepatitis
OCP ineffective
S/Es of isoniazid
Hepatitis
Peripheral neuropathy
S/Es of Ethambutol
Optic neuropathy
S/Es of pyrazinamide
Gout
What is the purpose of TB contact tracing?
Identify the source and identify transmission
What does the likelihood of infection with TB depend on?
Duration of contact
Intensity ofinfection
Who should have no immunity to tuberculoprotein?
< 16 y/o
no BCG
What is the vaccination against TB called?
BCG
What tests are done to screen for TB?
Mantoux test
Heaf test
Tuberculin test
If heaf +ve, what must be done next?
CXR
What must be done if heaf -ve?
Repeat after 6 weeks
If still -ve, give BCG
If +ve, Tx as recent infection
What is the 5 year survival with patients with cavitating disease?
25%
How long must TB drug treatment continue for?
At least 6 months
Types of TB disease
Primary
Secondary
Features of primary TB
Non immune host exposed to the mycobacterium may develop primary infection of the lungs
What happens in primary TB?
Small lung lesion called Ghon focus develops
Immunocompetent - healing by fibrosis
Immunocompromised - may develop disseminated disease (miliary TB)
What is a ghon focus made up of?
Tubercle-laden macrophages
What is a Gohn complex?
Ghon focus and hilar lymph nodes
Features of secondary (post primary) TB
Host becomes immunocompromised the initial infection may be reactivated
Where does reactivation generally occur?
Apex of the lungs
May spread to local or distant sites
Examples of causes of immunocompromise
Immunosuppressive drugs
HIV
Malnutrition
Where is the most common site for secondary TB?
Lungs
Main test used to screen for latent TB
Mantoux test
False negative tests in the Mantoux may occur when?
Miliary TB Sarcoidosis HIV Lymphoma Very young (e.g. < 6 months old)
Contraindications to BCG
Previous BCG Past history of TB HIV Pregnancy Positive tuberculin, heaf or mantoux
What test is offered to all patients with TB?
HIV testing
What can cause a reactivation of TB?
Immunosuppressant therapy such as chemo or biological treatments
