Tuberculosis

Question 1

Which of the following statements regarding the immune response to TB is NOT correct?
a. Macrophages are involved in immune control of the disease.
b. In TB, granulomas typically form as a result of a low antigen load and high tissue hypersensitivity.
c. T lymphocytes are involved in immune control of the disease.
d. Antibodies play an important role in host defence against TB.

Answer 1

Answer: b
PERSISTENT antigen load and a DELAYED-type hypersensitivity (Type 4).

• Granulomas = Hallmark lesions of TB
• Granulomas - form as the immune system attempts to wall off and contain Mtb infection.
• Host cells for Mtb = Macrophages

Question 2

Which one of the following statements regarding acquisition of TB is NOT correct?
a. Infected children between the ages of 2 and 14 years represent a group that has a relatively low chance of developing active TB.
b. About 35% of people infected with TB will develop clinical TB within the first 2 years after infection.
c. Droplet nuclei are infectious particles that are aerosolised by coughing, talking and sneezing.
d. Transmission occurs mainly by inhalation of infected particles.

Answer 2

Answer: b
Only 3% of people infected with TB will develop clinical TB within the first 2 years.

Immunocompetent:
* 3% (2 years) = Primary disease
* 97% = Latent TB infection = 7% risk of reactivation in lifetime

Immunocompromised (HIV):
* 30% = Primary disease
* 70% = Latent TB infection = risk 10% per annum of reactivation

Question 3

Which one of the following statements regarding gastrointestinal TB is NOT correct?
a. In patients with gastrointestinal TB it is usual to also have signs and symptoms of pulmonary TB.
b. The patient may present with bowel obstruction.
c. TB peritonitis causes an exudative ascites in which lymphocytes predominate.
d. The ileo-caecal junction is the commonest site of bowel involvement.

Answer 3

Answer: a
Evidence of pulmonary TB is present in less than 20% of patients.

TB GIT:
* Symptoms: Ascites, Peritonitis, Diarrhoea, Enteric ulceration, Perforation of bowel, Bowel obstruction, Mass formation, Abscess formation with fistulae
* Any sit from the mouth to the anus can be involved.
* The most common site of bowel involvement in TB is the ileo-caecal junction.
* Diagnosis is made by colonoscopy, laparoscopy or biopsy of intra-abdominal organs.
* Peritonitis causes an exudative ascites with a lymphocyte cellular predominance.
* Tuberculosis is a frequent cause of granulomatous hepatitis and is associated with elevated canalicular enzymes.

Question 4

Which one of the following is NOT a typical sign or symptom of TB?
a. Night sweats
b. Anorexia
c. Enlarged and painful lymph nodes
d. Chest pain

Answer 4

Answer: c
Lymph nodes are enlarged, firm and painless

• Key signs and symptoms of TB - wasting, anaemia, loss of lean and fat mass etc. - TB results in anorexia, cachexia, and generalised wasting
• Chest pain due to pleural involvement, inflammation, or persistent coughing

Question 5

Which one of the following statements regarding TB of the central nervous system (CNS) is NOT correct?
a. Diagnosis is dependent on lumbar puncture because acid-fast TB bacilli are abundant in the CSF.
b. CNS TB may present with vomiting.
c. Intracerebral tuberculosis vasculitis can lead to stroke.
d. Mortality from CNS TB is high in young patients under 5 years of age and in adults over 50 years of age.

Answer 5

Answer: a
Diagnosis is made on lumbar puncture BUT acid-fast bacilli are RARELY seen” (pg. 5 - TB Clinical presentations)