TB Flashcards
What causes TB
Mycobacterium TB (bacillus)
- M. TB = human only known reservoir
- M. bovis
- MOTT if immunocompromised
What are the RF for TB
Age - elderly Non-UK Known contact with someone with TB HIV - often pushes into active Immunosuppression - knocks latent into active - DM - HIV - Biologics - Anti-TNF - Organ tranplant Chronic renal Malignancy IVDA / alcohol Previous TB Decreased socio-economic ocnditions Malnutrition
What is the source of TB
Open active pulmonary TB cavitating lesion
Transported via resp droplets e.g. cough / sneeze
Two options
- Clear infection = 70% (phagocytksed by macrophages which kill as part of innate)
- Develop primary TB if unable to clear = 30%
What is mycobacterium TB
AAFB so requires ZN stain
Obliqate aerobe - requires O2
Faculative intracellular - prefers in cell e.g. macrophage but doesn’t have to be
What is primary TB and what is it associated with ?
1st infection if macrophages unable to clear
Lungs most commonly affected = 85%
Associated with development of immunity to tuberculoprotein (Mantoux test)
What happens when TB enters hilia of lungs
If infection clears or if primary develops
Macrophage ingest
Release cytokines to attract inflammatory cells
Antigen presenting cells present to CD4 lymphocyte in LN
MHC2 activated and go back to alveoli and kill TB
If this occurs = infection clears and no TB
Primary TB
Epitheliod granuloma forms (collection of macrophage) = Ghon focus
Often caesating - lots of necrosis
Langerhan’s giant cells produced
Can then spread via lymphatics to involve hilar node = Ghon complex
RANKE = focus + complex together
Disease can be contained here latent
What are in Langerhan’s
Macrophages
Found in every granulomatous condition e.g. sarcoid / vasculitis
What and where does primary TB affect
Children
Sub pleural area / UL
What does primary TB present with
Peripheral area of consolidation + hilar lymphadenopathy
Known as Gohn’s complex
What are granulomas
Central area of necrosis due to dead TB
Can calcify
Langerhan’s surround
What are the S+S of primary Tb
Asymptomatic in majority Fever Malaise Erythema nodosum Rarely chest sign
What can happen after primary infection
Primary progressive
Contained latent in lung if T cell response restricts (5-10% of reactivation but not contagious)
Reactivation - usually precipitated by alteration in immune. Can occur in pulmonary and extra-pulmonary site and most common form of active TB in clinic
What can happen after primary infection if don’t clear = primary progressive
If immune unable to suppress infection = TB pneumonia + risk of widespread dissemination (5%)
Usually if inadequate T cell immunity e.g HIV
Progressive consolidation
Bronchiectasis as bronchi collapse due to compression from LN
Pleural effusion
Bronchopneumonia if LN discharge
Hameatagenous spread - miliary and meningeal TB if poor immune
Miliary TB
- Disseminated TB characterised by military changes
Will be fatal if not treated
What are signs of miliary TB
Can be primary TB or reactivation Fine mottling on CXR Small granulomas throughout lung Spread through venous system 100% mortality if not treated Can spread through arterial but would appear septic
What is post primary TB
Reactivation of mycobacterium from latent primary infection
Disseminated by blood
Affects all organs but lungs most common in apex / UL
Who is at risk of post primary TB
Elderly Immunocompromised HIV Organ transplant Lymphoma Drugs - cytotoxic / steroid / biologics IVDU Haemodialysis Malnutrtion DM
What are the symptoms of post primary
Asymptomatic Fever FAtique Weight loss Night sweats Cough Haemoptysis Sputum Pleuritic chest pain SOB Dull ache Finger clubbing Erythema nodosum Lymphadenopathy Crackles Bronchial breathing Signs of effusion and fibrosis Low SATS Systemically unwell
Can get TB in any organ so high degree of suspicion
e.g. if GI = abdominal pain and commit
How do you investigate active TB
CXR = essential for Dx of pulmonary
Bloods - FBC, U+E, LFT
HIV test for all Dx
To Dx active need tissue / fluid
Early morning sputum to try isolate - 3 samples
- Sputum culture = gold standard but 4-6 weeks
- Microscopy for ZN stain will show in 48 hours
- Can do PCR but not routine
- If sputum +ve suggest highly infectious
Other test BAL - ZN stain / PCR Biopsy of LN / liver or areas that don't produce fluid CT thorax - Not everyone needs but useful to see extent of disease Mantoux test Bronchoscopy + biopsy Pleural aspiration
What does CXR show
Fibrosos and cavitatation Patchy shadows / infiltrates Pleural effusion Hilar lympahdneopathy Loss of volume Fibrosis Cavitation / calcification in upper zone if reactivated Miliary TB = millet seeds throughout lungs
How do you check for immunity / latent TB
Mantoux test = intradermal admission of tuberculoprotin results in inflammation after 24 hours
Delayed type 4 reaction
Can also do IGRA which is a blood test
Not affected by previous BCG vaccine or non-TB mycobacteria
If <6mm
Mantoux -ve
Give BCG vaccine
6-15mm
Sensitive to tuberculin
Shows past BCG vaccine or latent or active TB
> 15mm
Suggests very active TB - requires CXR
What must you do for all TB cases
Notify public health Test for HIV Test for Hep B+C Screen contacts - ExplsoreSx of active disease - Invite to undergo testing for latent
What is prophylaxis treatment of TB
BCG vacine
Signs of extrapulmonary TB
Most TB is lung as plenty of oxygen as aerobic organism TB meningitis Vertebrae = Pott's Cervical LN Renal / GI Cutaneous TB
How do you treat active TB
Isolate for 2 weeks -ve pressure rooms can be used in hospitals Rifampicin Isonazid Ethambutol Pyrazinamide 2 months of all 4 agents 4 months extra of izonzaid and rifampicin Add corticosteroid if CNS or pericardial
SE of drugs
Rifampicin
- Orange tears/ secretions
- Induce p450
- GI / de-ranged LFt but hepatotoxicity rare
- Check drugs and monitor LFT
Isonazid
- Peripheral neuropathy
- p450 inhibitor
- Liver injury
- Skin reaction / seizure
- Agranulocytosis
- Monitor LFT and do hepatitis liver screen
Ethambutol
- Optic neuropathy leasing to colour blindness and reduce visual acuity (check acuity before and during)
- Hyperuric and nephritis
Pyrazinamide
- Gout due to hyperuric
- Arthralgia
- GI upset and transient LFT
- Use caution if gout or liver disease
All except ethambutol = risk of hepatitis
When are you considered non-infectious
2 weeks
Rx of latent TB
3 months Isonazid and Rifampicin OR
6 months Isonazid
-Only option if HIV +ve
Balance Rx with SE of drugs
Treat if at risk of active e.g. HIV, transplant, chemo, biologics, younger age
How do you treat Meningeal TB
12 months Rx
Steroid
When should you suspect TB in chronic cough
If been put on immunosuppresion / biologics
Can reactivate
Do CXR
Who gets BCG vaccine
Neonates in areas with high risk TB Neonates with family from area of high risk TB Neonates with FH of TB Unvaccinated people with close contatc Healthcare worker
What do you do before BCG
Mantoux test
Vaccine only if test is -ve
What is the vaccine
Live attenuated so must exclude any immunosuppression / HIV
What could cause a false -ve Mantoux result
Immunosuppression - steroid / HIV Sarcoidosis Lymhpoma Age extreme Fever Hypo-albumin
What is needed before starting Rx
FBC - baseline as hepatotoxic so platelet
U+E
LFT - as all hepatotoxic
Vision testing - Ethambutol
Where can TB affect
Pulmonary Extrapulmonary - CNS - LN - Pericardium - GI / GU - Bones and joints - Cutaneous
What is classic cutaneous
Painful node on face
Known as lupus vulgaris
If pulmonary Sx + face lesion = think TB
What are constitutional Sx
Fever Weight loss Night sweats Reduced energy Reduced appetite
What are lung Sx
Cough
Chest pain - pleurite
SOB
Haemoptysis
Key DDX
Lung cancer
Bone and joint Sx
Back pain
TB spondylitis = Pott’s
Swelling
CNS Sx
Headache
Altered mental
CN palsy
What are LN Sx
Painless, rubbery lymphadenopathy
Usually cervical chain / supraclavicular
Can develop lymphadenitis
What causes night sweats
Usually suggestive of underlying malignant / infectious / inflammatory process
Ddx of granuloma
TB
Sarcoid
Vasculitis
If Mantoux test +Ve what do you do
Reassess for signs of active TB
CXR
HIV test
What can BCG be used for
Bladder cancer
Mod / high risk non-muscle invasive
What is MDR TB
Resistance to two 1st line Rx
What is XDR TB
Resistance to 2nd line options of fluoroquinolone and injection
