L5 Pathology of Pulmonary Tuberculosis

Question 1

Which patients are most commonly affected by M. avium intracellulare ?

Answer 1

AIDS patients

Question 2

Which are the factors that increase the risk of developing TB ?

Answer 2

• Low socioeconomic status
• Crowded living conditions
• Immune deficiency disorders
• Immunosuppressive therapy
• Health care workers
• Alcoholism
• Malnourishment
• Hodgkin lymphoma
• Diabetes
• Chronic pulmonary lung disease ( silicosis )

Question 3

What is the organ involvement of TB ?

Answer 3

1. Pulmonary ( lungs ), 85% of the cases
2. Extra-pulmonary
   - GI
   - GU
   - joints and bones
   - lymph nodes
   - skin: lupus vulgarus
   - meninges

Question 4

Why M. Tuberculosis resist decolorization of acid and alcohol ?

Answer 4

Due to the thick mycolic acid layer in the wall

Question 5

What are transmission mechanisms of mycobacterium?

Answer 5

1. Droplet infection (with active pulmonary TB)
2. Swallowing the infected saliva after coughing it
3. Ingestion of (M. bovis in unpasteurized milk)
4. Inoculation
5. Transplacental ( rare )

Question 6

What are the factors that determine the development of clinical disease ?

Answer 6

1. Number of inhaled organisms
2. Virulence of the organisms
3. The infective dose that is required to cause the disease
4. The development of ( anti-mycobacterium) cell-mediated immunity

Question 7

What is primary TB ?

Answer 7

It is infection of unexposed person ( for the first time )
1. Ghon focus …. sub plural granuloma only

2. Ghon complex :
   - sub plural granuloma
   - hilar lymph node granuloma
   - lymphangitis

Most commonly resolve leaving calcification and fibrosis

Question 8

What are the histopathological features of granuloma ?

Answer 8

1. Progression:
   - Caseating
   - Non-caseating
2. No progression ( latency )
3. Healing by fibrosis and calcification ( calcification appears in radiograph as ranke complex )

Question 9

What is the Fate of Primary TB ?

Answer 9

1. Healing (95% cases)
   • Resolution
   • Fibrosis & Calcification
2. Primary Progressive disease < 5%
   * pneumonia
   * cavity formation
   * pleurisy
   * miliary TB
   * extra-pulmonary spread

Question 10

What is the classic lesion of TB ?

Answer 10

Caseous granuloma

Question 11

What is secondary TB ?

Answer 11

It is infection in previously exposed person

1. Reactivation of endogenous ( mostly )
   - aging
   - reduced immunity
2. Re-infection / exogenous ( rare )

Question 12

What is the Fate of secondary TB lesion ?

Answer 12

• pneumonia
• cavity formation
• pleurisy
• miliary TB
• extra-pulmonary spread ( hematogenous )
• fibrosis/ scarring and calcification

Question 13

What are the methods of extra-pulmonary spread ( which is a complication of both primary and secondary ) ?

Answer 13

1. Hematogenous ( to many organs )

2. Direct spread by swallowing of saliva ( GI TB )

Question 14

What is Miliary tuberculosis (TB) ?

Answer 14

Miliary tuberculosis (TB) is the widespread dissemination of Mycobacterium tuberculosis via hematogenous spread and it is a complication of both primary and secondary TB

Question 15

What is the name of MTB appearance ?

Answer 15

Ground-glass appearance

Question 16

What are the organs that are affected by MTB ?

Answer 16

1. Lung
2. Pleura
3. Liver
4. Spleen
5. Kidney
6. Meninges
7. BM ( pancytopenia )

Question 17

What are the risk factors of MTB ?

Answer 17

1. Extremes of Age

2. Immunosuppression
• Cancer 
• Organ Transplantation 
• HIV
• Malnutrition 
• Diabetes

Question 18

Why diabetes cause low immunity ?

Answer 18

Due to low insulin and high sugar in blood