TB

Question 1

Initial infection with mycobacterium tuberculosis (primary infection), where does this usually occur?

Answer 1

upper region of the lungs producing a sub pleural lesion
called the Ghon focus

Can also occur in GI tract (rare)

Question 2

Describe the pathophysiology of the primary infection?

Answer 2

Primary focus is characterised by exudation and infiltration with neutrophil granulocytes

These are replaced by macrophages which engulf the bacilli and results in typical granulomatous lesions

Accompanied by granulomatous lesions in regional lymph nodes.

Usually primary infection clears & regional lymph nodes heal and calcify. However lymph nodes still usually harbour some tubercle bacilli; may become reactivated if immunocompromised

Question 3

What does a typical granulomatous lesion look like in TB?

Answer 3

Central areas of caseation surrounded by epithelioid cells (macrophages that look like epithelial cells) and langerhans giant cells

Question 4

What is miliary TB?

Answer 4

Dissemination (spread) of primary TB

Question 5

TB epidemiology?

Answer 5

Biggest killer out of infectious diseases

Most common cause of death in HIV patients

Question 6

How does pulmonary TB present?

Answer 6

May be silent, OR: 
cough 
weight loss
sputum 
malaise
night sweats 
Pleurisy 
Haemoptysis 
Pleural effusion

Question 7

Miliary TB?

Answer 7

Occurs following haematogenous dissemination

Signs may be non specific and overwhelming

Question 8

Genito-urinary TB?

Peritoneal TB?

Answer 8

Dysuria, frequency, loin/back pin, haematuria, sterile pyuria (puss in urine)
Renal TB may spread to bladder, seminal vesicles, epididymis or Fallopian tubes

Abdo pain, GI upset, AFB in ascites

Question 9

Bone TB?

skin TB?

Answer 9

Vertebral collapse and Pott’s vertebra

Jelly like nodules on face/ neck

Question 10

Diagnostic tests and results for latent TB?

Answer 10

Mantoux test- tuberculin sensitivity test,

if positive consider IFN-gamma testing

Question 11

Diagnostic tests and results for active TB?

Answer 11

CXR

Sputum samples; 3 positive results needed before starting treatment
Bronchoscopy and lavage may be needed if not spontaneously producing sputum

For active non respiratory TB: Sputum, pleural fluid, ascites, pus, urine, bone marrow or CSF samples

Question 12

What CXR signs are there in TB?

Answer 12

Consolidation
Cavitation
Fibrosis
Calcification

Question 13

What immunological evidence is there for TB?

Answer 13

Tuberculin sensitivity skin test: TB antigen injected intradermally and cell-mediated response at 48-72h is recorded.
+ve test indicated immunity – also previous exposure/ or vaccination. Strongly +ve test = active TB

Quantiferon TB gold and T-spot TB (IFN-gamma tests) are better than tuberculin skin tests

Question 14

Compliance is crucial in treatment for TB and direct observed therapy is usually carried out. What medication is given?

Answer 14

For first 2 months: Isoniazid, Rifampicin, Pyrazinamide and ethambutol
Isoniazid and Rifampicin are continued for further 4 months

Question 15

Side effects for TB drugs??

Answer 15

Rifampicin; raised LFTs, low platelet count, orange discolouration of urine, tears and contact lens, inactivation of the pill and flu symptoms

Isoniazid; raised LFTs, low WCC, neuropathy (stop- give pyridoxine)

Ethambutol; optic neuritis

Pyrazinamide; hepatitis, arthralgia, CI in active gout, porphyria.