Week 10 - Tuberculosis

Question 1

What is Tuberculosis (TB)?

Answer 1

A chronic infectious granulomatous disease caused by Mycobacterium tuberculosis, mainly affecting the lungs, but can spread to other organs (extrapulmonary TB).

Question 2

What is the etiological agent of TB and its key characteristics?

Answer 2

Mycobacterium tuberculosis

Rod-shaped, non-motile, obligate aerobe

High lipid cell wall (acid-fast positive, not Gram +/–)

Hydrophobic surface

Survives inside macrophages

Question 3

How is TB transmitted?

Answer 3

Through airborne droplets released when an infected person coughs, sneezes, or speaks. Droplets are inhaled into alveoli where infection begins.

Question 4

What are the major global problems associated with TB?

Answer 4

1/3 of the world’s population infected

Leading killer of people with HIV

Rise of MDR-TB and XDR-TB

Risk factors: crowding, poverty, HIV/AIDS

Question 5

What is the pathogenesis of TB?

Answer 5

Inhaled bacilli reach alveoli → engulfed by macrophages

Bacilli survive intracellularly and multiply

Immune response (T-cell mediated) forms granulomas

Strong immunity → latent TB

Weak immunity → active TB (local or disseminated)

Question 6

How does immunity affect TB severity?

Answer 6

TB is most severe in people with poor immunity (infants, elderly, malnourished, HIV-positive).

HIV and TB act synergistically, worsening each other.

Weak immunity allows miliary spread via blood or bronchopneumonia in lungs.

Question 7

What is a Ghon focus and Ghon complex?

Answer 7

hon focus: Localized primary lesion in lung parenchyma.

Ghon complex: Ghon focus + involved hilar lymph node.

Commonly found in primary TB.

Question 8

What are the differences between Primary and Secondary TB?

Answer 8

Primary TB:
Exposure: First infection
Site: Lower/mid lung zones
Lesion: Ghon focus/complex
Symptoms: Usually asymptomatic

Secondary TB:
Exposure: Reactivation or reinfection
Site: Apex of lung
Lesion: Cavitary lesions
Symptoms: Cough, fever, weight loss

Question 9

Describe Primary TB.

Answer 9

Occurs in those with no previous exposure.

Ghon focus/complex forms in lungs and lymph nodes.

90% heal and become latent; 10% progress to miliary or bronchopneumonia in weak immunity.

Question 10

Describe Secondary TB.

Answer 10

Occurs in previously infected individuals due to reactivation or reinfection.

Triggered by HIV, cancer, chemotherapy, or old age.

Causes localized cavitation, cough, haemoptysis, weight loss, fever.

May spread to other organs (miliary TB).

Question 11

What are the key pathological features of TB?

Answer 11

Granulomatous inflammation (tubercles)

Caseous necrosis in the center

Langhans giant cells and lymphocytes surrounding necrosis

Cavitation in secondary TB

Miliary nodules in disseminated disease

Question 12

What is Miliary TB?

Answer 12

A disseminated form of TB due to spread of bacilli through the bloodstream, producing numerous small granulomas in multiple organs.

Question 13

What is Latent TB?

Answer 13

Occurs when the immune system contains infection but does not eliminate bacilli.

Person is asymptomatic and non-infectious.

Can reactivate if immunity declines.

Question 14

How is Latent TB diagnosed?

Answer 14

Mantoux (PPD) skin test: intradermal tuberculin reaction

IGRA (Interferon Gamma Release Assay): detects immune sensitization, not affected by BCG vaccination

Question 15

What are the clinical features of Active TB?

Answer 15

Cough (persistent, purulent, or bloody)

Fever, night sweats, weight loss, malaise, anorexia

Haemoptysis in ~50% of cases

Chest pain and breathlessness in pulmonary involvement

Question 16

What are the extrapulmonary sites where TB can occur?

Answer 16

Lymph nodes (25%)

Kidneys

Adrenal glands

Bones (esp. spine)

Meninges

Intestines

Fallopian tubes

Pleura

Question 17

What are the main diagnostic tests for TB?

Answer 17

Chest X-ray

Sputum smear (acid-fast stain)

Sputum culture (gold standard)

PCR (NAAT)

Mantoux/PPD test

IGRA (blood test) – unaffected by BCG

Question 18

Which diagnostic test is the gold standard for TB?

Answer 18

Sputum culture for Mycobacterium tuberculosis from the affected site.

Question 19

What are the first-line anti-TB drugs?

Answer 19

Isoniazid (INH)

Rifampin (RIF)

Pyrazinamide (PZA)

Ethambutol (EMB)

Question 20

What are the second-line anti-TB drugs?

Answer 20

Levofloxacin

Moxifloxacin

Used for MDR-TB or XDR-TB cases.

Question 21

What are MDR-TB and XDR-TB?

Answer 21

MDR-TB: Resistant to isoniazid and rifampin (first-line drugs).

XDR-TB: Resistant to both first- and second-line drugs.

Caused by poor adherence to therapy.

Question 22

What is Directly Observed Therapy (DOT)?

Answer 22

A TB control strategy where healthcare workers observe patients taking medications to ensure adherence and prevent resistance.

Question 23

What are the main preventive measures for TB?

Answer 23

BCG vaccination

Avoid contact with active TB cases

Adequate ventilation and hygiene

Early detection and treatment

Ensure full drug course compliance (DOT)

Question 24

What populations are most at risk for TB?

Answer 24

Infants and elderly

HIV/AIDS patients

Malnourished individuals

Overcrowded and impoverished communities

Immunosuppressed (e.g., organ transplant, chemotherapy)

Question 25

What are the possible outcomes of untreated secondary TB?

Answer 25

Fatal if untreated due to tissue destruction and spread. Curable with appropriate prolonged antibiotic therapy. Risk of drug resistance if medication course is incomplete.