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Pulmonary system > Pathology of Tuberculosis and Fungal Infection > Flashcards

Pathology of Tuberculosis and Fungal Infection Flashcards

1
Q

Tuberculosis I -characteristics

A
  • communicable
  • chronic
  • granulomatous (typically granulomas undergo caseous necrosis)
  • usually involves the lung but may affect any organ in the body
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2
Q

Cause of TB I

A

Mycobacterium tuberculosis

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3
Q

Tuberculosis IV reservoir

A

-in humans with infection/disease

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4
Q

Tuberculosis IV transmission

A
  • inhalation of airborne organisms in aerosols from infected person
  • exposure to aerosolized contaminated secretions
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5
Q

Primary pulmonary TB -mechanism developement first 3 weeks

A

-mannose-capped glycolipid on mycobacterium binds to macrophage mannose receptor on airway macrophage
-mycobacterium enters the macrophage
-inside mycobacterium causes endosomal manipulation :
a) maturation arrest
b) lack of acid pH
c) ineffective phagolysosome formation
so can survive in the cell and get unchecked bacillary proliferation
-bacteremia with seeding to multiple sites

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6
Q

Primary pulmonary TB -mechanism development past 3 weeks

A

1) Infected alveolar macrophage activates naive T-cell
(presenting MTB antigen on class II MHC to the T-cell receptor + IL-12)
2) naive T cell differentiates to TH1
3) TH1 releases IFN-y whch activates macrophages
4) Activated macrophage secretes TNF. chemokines, nitric oxide and free radicals
5) TNF, chemokines lead to monocyte recruitment
4) Causes caseous necrosis, and sensitized T cell (epithelioid granulom)

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7
Q

Why does TB survive in the body

A

Cell mediated immunity confers resistance to the organism

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8
Q

Consequence of TB survival in the body

A

-cell mediated immunity results in developmet of tissue hypersensitivity to tubercular antignes

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9
Q

Cause of pathological features of TB i.e. caseating granulomas and tissue cavitation

A
  • result of destructive tissue hypersensitivity that constitutes the host immune response
  • i.e. the immune response comes at the cost of hypersensitivity and accompanynig tissue destruction
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10
Q

Primary TB I -in who it develops

A

-develops in previously unexposed person

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11
Q

Source of organism in Primary TB 1

A
  • exogenous source

- typically inhaled bacilli implant in distal air spaces of lower part of upper lobe or the upper part of the lower lobe

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12
Q

Location of bacilli in primary TB 1

A

-inhaled bacilli implant in distal air spaces of lower part of upper lobe or upper part of lower lobe (usually close to the pleura)

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13
Q

Ghon focus

A
  • a 1- 1.5 cm area of grey-white inflammatory consolidation

- happens when sensitization develops in primary TB II

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14
Q

Ghon complex

A

-combination of parenchymal lesion (ghon focus) and nodal involvement (as TB drain to regional lymph nodes which also often caseates)

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15
Q

Primary TB III characteristics

A

-during first few weeks also get lymphatic and hematogenous dissemination to other parts of the body

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16
Q

Ghon complex in primary TB III

A
  • undergoes progressive fibrosis

- often followed by radiologically detectable calcification

17
Q

Primary TB IV -characteristics

A
  • foci of scarring may harbour viable bacilli for years –> potential for reactivation at a later time when host defences compromised
  • uncommonly the disease may develop into so-called progressive TB
18
Q

When progressive primary TB occurs

A
  • in immunocomprommised states:
    a) malnourishment
    b) elderly age group
    c) AIDS
    d) certain racial group ie Inuit
19
Q

Why progressive primary TB occurs

A

-immunosuppression leads to inability to mount CD4+ T-cell mediated immunologic reacion that would contain the primary focus

20
Q

Consequences of progressive primary TB

A
  • miliary tuberculosis

- tuberculous meningitis

21
Q

Miliary tuberculosis

A

X

22
Q

Tuberculous meningitis

A

X

23
Q

Secondary tuberculosis I -what is it

A

-the pattern of disease that arises in a previously sensitized host

24
Q

Causes of secondary tuberculosis I

A
  • Arises from reactivation of dormant primary lesions
  • usually when host resistance is weakened but also from exogenous re-infection
  • usually many decades after initial infection
25
Q

Location of secondary tuberculosis II

A

-classically localized to the apex of one or both upper lobes

26
Q

Reason for secondary TB II

A

-may related to high oxygen tension in the apices

27
Q

Consequences of secondary TB II

A
  • cavitation occurs readily in the secondary form

- results in dissemination along the aiways

28
Q

Source of infectivity in secondary TB II

A

-erosion into an airway –> person raising sputum containing bacilli

29
Q

Secondary TB III characteristics

A
  • initial lesion less than 2 cm in diameter (within 1-2 cm of apical pleura)
  • variable amount of central caseation and peripheral fibrosis
30
Q

Secondary TB IV characteristics

A
  • localized apical secondary pulmonary TB

- may heal with fibrosis spontaneously or after therapy or disease may progress along several different pathways

31
Q

Complications of secondary pulmonary TB 1

A
  • progressive pulmonary tb
  • erosion into bronchi with cavitation
  • blood vessel erosion results in hemoptysis
  • miliary pulmonary disease
  • pleural efffusion/tb empyema
  • endobronchial, endotracheal laryngeal TB
32
Q

Complications of secondary TB II

A
  • systemic miliary TB
  • isolated-organ tb including tb meningitis
  • lymphadenopathy, usually cervical region (scrofula)
  • death
33
Q

Strains causing nontuberculous mycobacterial disease in immunocompetent host

A

Strains

  • mycobacterium avium complex
  • mycobacterium kanasasii
  • mycobacterium abcessus
34
Q

Presentation of nontuberculous mycobacterial disease in immunocompetent host

A

-upper lobe cavitary disease (mimicks TB)

35
Q

Risk factors of nontuberculous mycobacterial disease -immunocompetent host

A
  • chronic obstructive pulmonary disease
  • cystic fibrosis
  • pneumoconioses
36
Q

Nontuberculous mycobacterial disease-immunocompromised host (primarily HIV positive disease) -I presentation

A

1) Mycobacterium avium complex - presents as disseminated disease with systemic symptoms (fever, night sweats, weight loss)
- hepatosplenomegaly and lymphadenopathy (involvement of mononuclear phagocyte system are common)
- gastrointestinal symptoms such as diarrhea and malabsorption also common
- pulmonary involvement often indistinguishable from tuberculosis in AIDS patients

37
Q

Nontuberculous mycobacterial disease -immunocompromised host (primarily HIV positive disease)-II

A
  • disseminated mycobacterium avium complex infection in AIDS patients tends to occur late in the disease when CD4 count is less than 100 cells/mm3
  • tissue examination usually dose not reveal grnulomas
  • proliferation of foamy macrophages “stuffed” with atypical mycobacteria
38
Q

Multidrug resistance tuberculosis (MDR-TB)

A

-MDR-TB is defined as resistance of mycobacteria to two or more of the primary drugs used for treatment

39
Q

Prognosis of TB

A
  • favorable if infection localized to lungs
  • worsens significantly in
    a) aged
    b) debilitated
    c) immunocompromised
    d) MDR-TB

Pulmonary system (19 decks)

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