Tuberculosis Flashcards
Aetiology of tuberculosis
Mycobacterium tuberculosis
- Aerosol droplets
Mycobacterium bovis
Mycobacterium africanum
Where can TB affect
Lungs (pulmonary TB)
Lung Pleura - pleural effusion (usually unilateral)
Lymph
Spine (Pott’s)
Miliary (blood)
Brain:
- Tuberculomas (Ring-enhancing lesion)
- Meningitis
Eye: uveitis
Laryngeal TB
Pericardium
Adrenals (adrenal insufficiency)
Skin (to cause erythema nodosum, lupus vulgaris)
Bone and joints (Poncet’s - generalised inflammation as a reaction to TB antigens)
Genito-urinary - infertility due to fallopian tube involvement
GIT - Terminal ileum affected (very hard to differentiate from Crohn’s - also shows granulomas) - can present with ascites
Active vs latent TB
Active: symptomatic or progressive disease
- Infection with M. tuberculosis and inadequate containment by the immune system
Latent: persistent immune response to M. tuberculosis antigens with NO evidence of clinically active TB
- no clinical, bacteriological, or radiographic evidence of active TB
- Due to granuloma formation that prevents bacterial growth and spread
Risk factors for TB infection
Exposure to infection
HIV-infected individuals
Birth in or travel to an endemic country (South Asia, India, Bangladesh, Pakistan, Romania, Somalia)
Immunosuppressive medicines e.g. corticosteroids, chemotherapy, anti-TNF
Silicosis
Apical fibrosis
Recent tuberculin skin test conversion
Deprivation
IVDU
Cigarette smokers
Immunocompromised individuals e.g. diabetes, prolonged corticosteroid use, end-stage renal disease, malnutrition, haematological malignancy
Symptoms of tuberculosis
Primary TB is usually asymptomatic
Cough
- longer 2-3 weeks, initially dry then later productive
- Haemoptysis
Fever
Malaise
Weight loss or anorexia
Pleuritic chest pain
Dyspnoea
Night sweats
Psychological symptoms (depression, hypomania)
Joint/spinal TB: bone/joint pain, back pain, joint swelling
TB meningitis: Headache, vomiting, irritability, confusion
TB pericarditis: breathlessness, chest pain, ankle swelling
Differentials for tuberculosis
S/S: pneumonia, COPD, asthma, lung malignancy, lung fibrosis
Ring enhancing lesion: Tuberculoma, toxoplasmosis, lymphoma
Erythema nodosum: Strep, malignancy, sarcoidosis, IBD, OCP use
Signs of tuberculosis on examination
General exam
- Clubbing
- Erythema nodosum (reddish, painful, tender, lumps found commonly in the front of the legs on the calf)
- Erythema induratum (nodular vasculitis)
- HIV: oral candidiasis
Head and neck
- Lymphadenopathy: cervical, supraclavicular, painless, rubbery
Respiratory
- may be normal in mild/moderate disease
- crackles, bronchial breath sounds, or amphoric breath sounds (distant hollow breath sounds over cavities)
Investigations for active TB
Sputum sample for MC&S x3
- microscopy with Zihel-Neelsen stain
- Culture with Lowenstein-Jensen media
- Culture takes 1-3 weeks (liquid) or 4-8 weeks (solid)
- More sensitive than smears
Sputum smear for acid-fast bacilli
Sputum PCR - gene expert
FBC: raised WCC, anaemia of chronic disease, raised plt
CRP: raised
ABG: ? T1RF
LFTs: before starting TB drugs
U&Es
Blood culture
HIV serology
CXR: cavitating lesion | pleural effusion | mediastinal/hilar lymphadenopathy | patchy consolidation
LP: high pressure, high protein, low glucose, lymphocytosis
Lymph node biopsy: caseating granuloma
Abdo disease → AXR
neuro disease → MRI
Investigations for latent TB
Tuberculin skin testing (Mantoux)
- Size of skin induration is used to determine positivity depending on vaccination history and immune status (>5mm if risk factors, >15mm if no risk factors)
Interferon-gamma release assays (IGRAS)
Management for tuberculosis
- Assess need for admission
- Symptomatic/systematically unwell → hospital admission
- Well → urgent local TB MDT for confirmation (+ isolate at home until 5 days-2 weeks of therapy) - Notify local HPT
- Anti-TB therapy:
- Rifampicin - 6 months
- Isoniazid (with pyridoxine*) - 6 months
- Pyrazinamide - First 2 months
- Ethambutol - First 2 months - Contact tracing
Can adjust/step down once culture results are available (4-8 weeks)
If CNS TB: prolong treatment to 12 months
Bone TB: prolong to 9 months
pyridoxine prevents isoniazid-related peripheral neuropathy
What is multi and extensively drug resistant TB and how is it managed
Multidrug-resistant TB= resistant to rifampicin and isoniazid
Extensively drug-resistant TB = resistant to rifampicin, isoniazid, fluoroquinolones and at least 1 injectable
Treatment regimens are much longer (18-24 months) and have more drugs e.g. 7 drugs
Management for latent TB
Assess for active TB
Treat for latent TB using 3 months of isoniazid (with pyridoxine) and rifampicin
OR
Treat for latent TB using 6 months of isoniazid (with pyridoxine)
Complications of treatment for tuberulcosis
Rifampicin - hepatotoxicity, CYP inducer, orange fluids, purple tears (RIP)
Isoniazid - hepatotoxicity, peripheral neuropathy, anaemia, pericarditis, SLE (I can’t walk)
Pyrazinamide - hepatotoxicity, gout (Increased uric acid), photosensitivity (Painful joints)
Ethambutol - optic neuritis - test colour and acuity beforehand (Eye)
*RIP - Hepatotoxicity
Can get a paradoxical reaction - this would be detrimental in the brain and pericardium -> given steroids
Prognosis for tuberculosis
Untreated, active TB is a slowly progressive disease which may be potentially fatal (>50%), particularly if the diagnosis is delayed
TB is a treatable disease that may be cured. In general, most who are treated can expect to do well with minimal or no sequelae
Once latent, there is a 5–10% lifetime risk of progression to active (symptomatic) disease if, for example, the person becomes immunocompromised or has intercurrent illness
Increasing age, more extensive disease, and HIV co-infection are associated with a worse prognosis, recurrent infection and/or reinfection and increased mortality
Multi-drug resistant TB has poorer prognosis than fully drug-susceptible TB
