TB Flashcards
(24 cards)
Primary TB
naïve TB infection
- Organism multiplies at pleural surface → Ghon Focus
- Macrophages take TB to LNs - Ghon complex
- Mostly asymptomatic
- Rarely causes primary progressive TB but may occur in immunocompromised
Ghon complex
Nodes + lung lesion
Ghon Focus
TB Lung lesion
Ranke complex)
Fibrosis of Ghon complex → calcified nodule
Latent TB
Infected but no clinical or x-ray signs of active TB
- Non-infectious
- May persist for years
- Weakened host resistance → reactivation
Secondary TB
Usually reactivation of latent TB due to ↓ host immunity
- Typically develops in the upper lobes
- → cavitation and
formation of caseating granulomas
Clinical features of pulmonary TB
Cough, sputum Malaise Fever, night sweats, wt. loss Haemoptysis Pleurisy Pleural effusion Aspergilloma / mycetoma may form in TB cavities
Causative organism
Mycobacterium tuberculosis
Clinical features of meningeal TB
Headache, drowsiness Fever Vomiting Meningism - photophobia and neck stiffness Worsening over 1-3wks Papilloedema
GU TB
Frequency, dysuria, loin/back pain, haematuria
Sterile pyuria
Bone TB
Vertebral collapse and Pott’s vertebra
Ix
Bloods - FBC, U+Es, LFTs, CRP
Sputum culture x 3 and microscopy
Blood culture
CXR
Test for TB
Tuberculin Skin Test
IGRA - interferon gaba release assay
Signs of TB on CXR
Mainly upper lobes. Consolidation Cavitation Fibrosis Calcification
Stain for mycobacterium tuberculosis
Ziehl-Neelsen stain - show acid fast bacili
Tuberculin Skin Test
Intradermal injection of purified protein derivative
False +ve: BCG, other mycobacteria, prev exposure (latency)
Cannot distinguish between active and latent or vaccinated
Interferon Gamma Release Assays
Pt. lymphocytes incubated with M. tb specific antigens → IFN-γ production if previous exposure.
Will not be positive if just BCG (uses M. bovis)
Cannot distinguish between active and latent
Mx of TB
Mx w/o culture if clinical picture is consistent with TB
- Stress importance of compliance
- Check FBC, liver and renal function and eyes before medication
Mx: RIPE
- 2 months:
Rifampicin + isoniazid + pyrazinamide + Ethambutol
- 4 months:
Rifampicin and isoniazid
Contact tracing
Rifampicin s/e
hepatitis, orange urine, enzyme induction
Isoniazid s/e
hepatitis
Peripheral sensory neuropathy
Pyrazinamide
hepatitis, arthralgia
ethambutol
Optic neuritis
Meningeal TB Mx
Head CT
Examinations for meningism - Kernigs and Brudinski’s
RIPE - 2 months
Rifampicin and isoniazid - 10 months
Dexamethasone
Risk factors
Immigrant IVDU HIV Immunocompromised Homeless Close contacts Young adults and elderly
