Maxi CBL - Pulmonary TB

Question 1

What are the typical symptoms of pulmonary TB? [8]

Answer 1

1. Breathing difficulty
2. Chest pain.
3. Cough (usually with mucus)
4. Coughing up blood
5. Excessive sweating, particularly at night
6. Fatigue
7. Fever
8. Weight loss

Question 2

Which groups of people are at higher risk of developing pulmonary TB? [3]

Answer 2

1. Elderly men
2. People who grew up or visit areas of the world where TB is much more common
3. Patients who are HIV-positive

Question 3

What is the potential differential diagnosis of pulmonary TB? [1]

Answer 3

bronchial carcinoma

Question 4

What investigations should you carry out on a patient with suspected pulmonary TB? [5]

Answer 4

1. Sputum sample
   
   • examined for the presence of TB bacilli by special stains, typically the Ziehl-Nielsen stain.
2. CT scan of the chest
   
   • this can help differentiate between active TB and the presence of a bronchial neoplasm.
3. Bronchoscopy
   
   • this will detect any intra-airway neoplasm and also provide additional material for culture
   • the pleural effusion should be tapped and the pleural fluid examined for TB
4. Pleural biopsy
   
   • can also be helpful as it may show typical necrotising granulomas in TB
5. Biopsy under direct vision (thoracoscopy) or by image guidance has a higher sensitivity.

Question 5

Describe the standard treatment therapy for pulmonary TB, including which drugs are included and how these drugs are altered throughout the course of treatment [7]

Answer 5

1. Current standard therapy starts with 4 drugs with known good activity against TB (first-line drugs), which are:
   
   • rifampicin,
   • isoniazid,
   • pyrazinamide
   • ethambutol
2. Pyrazinamide has little activity against very slow growing bacilli and is thus dropped after 2 months when typically only very slow growing bacilli remain.
3. Once sensitivities of the TB are known, the ethambutol can also be dropped.
4. Rifampicin and isoniazid are continued throughout the duration of therapy, typically 6 months.

Question 6

What are the potential side effects of each of the TB drugs and how should they be monitored? [4]

Answer 6

1. Isoniazid can lead to a peripheral neuropathy due to antagonism of the effects of pyridoxine (Vitamin B6).
   
   • hence, pyridoxine treatment as a prophylactic measure is added to the standard regimen.
2. Rifampicin colours urine a red colour and is a potent inducer of hepatic cytochrome P450 enzymes that can lead to dramatic changes in the metabolism of numerous drugs that will thus require dosage adjustment.
3. Rifampicin, isoniazid, pyrazinamide are all potentially hepatotoxic and this can be rapid and profound requiring initial careful monitoring of therapy.
4. Ethambutol can affect vision, so visual acuity prior to starting treatment should be recorded to allow changes later to be evaluated better.

Question 7

What are the potential complications of TB (extra-nodal)? [9]

Answer 7

1. Nodal TB.
   
   • Cervical lymph nodes are typically involved.
2. Osteomyelitis.
   
   • TB has a predilection for vertebral bones
   • This can also then extend to form a spinal/paraspinal abscess with cord compression or extension into the sheath of the psoas muscle
3. CNS TB.
   
   • TB can spread into the brain and CSF giving two main types of infection:
     
     • TB meningitis,
       
       • a slowly progressive condition with altered conscious level and progressive lower cranial nerve palsies.
     • Cerebral TB.
       
       • foci of infection can behave like a space-occupying lesion, with seizures, nervous systemic signs etc.
4. Other organ systems that can be affected: renal tract including testes/ovaries, larynx, skin, eye, liver.