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Respiratory: Pathology > Pathology of Pulmonary Infections > Flashcards

Pathology of Pulmonary Infections Flashcards

1
Q

What is pneumonia?

A

Infection involving the distal airspaces usually with inflammatory exudation (“localised oedema”)

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2
Q

What do fluid-filled spaces caused by pneumonia result in?

A

Consolidation

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3
Q

What are classifications of pneumonia?

A
  • By clinical setting (e.g. community acquired pneumonia)
  • By organism (mycoplasma, pneumococcal etc)
  • By morphology (lobar pneumonia, bronchopneumonia)
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4
Q

What pathogens can cause pneumonia?

A
  • Viruses – influenza, parainfluenza, measles, varicella-zoster, respiratory syncytial virus (RSV).
  • Bacteria - Chlamydia, mycoplasma
  • Fungi
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5
Q

What is lobar pneumonia?

A

Confluent consolidation involving a complete lung lobe

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6
Q

What pathogen causes lobar pneumonia?

A
  • Most often due to Streptococcus pneumoniae (pneumococcus)

* Can also be caused by Klebsiella, Legionella

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7
Q

How are most cases of lobar pneumonia acquired?

A

Community acquired

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8
Q

What individuals are infected with lobar pneumonia?

A

Classically in otherwise healthy young adults

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9
Q

Describe the pathology of lobar pneumonia

A

A classical acute inflammatory response

  • Exudation of fibrin-rich fluid
  • Neutrophil infiltration
  • Macrophage infiltration
  • Resolution

Immune system plays a part - antibodies lead to opsonisation, phagocytosis of bacteria

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10
Q

Why is control of inflammation important in lobar pneumonia?

A

To prevent destruction of alveolar walls

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11
Q

What are histological characteristics of lobar pneumonia?

A
  • Congested capillaries due to increased blood flow
  • Alveolar lumens filled with neutrophils and macrophages
  • Thickened alveolar walls
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12
Q

What are complications of lobar pneumonia?

A
  • Organisation (fibrous scarring)
  • Abscess
  • Bronchiectasis
  • Empyema
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13
Q

Why is fibrous organisation dangerous?

A

Reduces capacity for gas exchange

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14
Q

What is bronchopneumonia?

A

Infection starting in airways and spreading to adjacent alveolar lung

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15
Q

What individuals are at risk of bronchopneumonia?

A

Most often seen in the context of pre-existing disease

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16
Q

What are risk factors for bronchopneumonia?

A
  • COPD (acute bronchitis due to exacerbation spreads pneumonia)
  • Cardiac failure (elderly)
  • Complication of viral infection (influenza)
  • Aspiration of gastric contents
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17
Q

What pathogens cause bronchopneumonia?

A

More varied – Strep. Pneumoniae, Haemophilus influenza, Staphylococcus, anaerobes, coliforms

(Staph/anaerobes/coliforms seen in aspiration)

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18
Q

What are the complications of bronchopneumonia?

A
  • Organisation
  • Abscess (v important)
  • Bronchiectasis
  • Empyema
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19
Q

What is an abscess?

A

Localised collection of pus (tumour-like)

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20
Q

What are symptoms of bronchopneumonia?

A

Chronic malaise and fever

21
Q

What is abscess formation associated with in bronchopneumonia?

A

Aspiration

22
Q

What is bronchiectasis?

A
  • Abnormal fixed dilatation of the bronchi

* Dilated airways accumulate purulent secretions

23
Q

What causes bronchiectasis?

A
  • Usually due to fibrous scarring following infection (pneumonia, tuberculosis, cystic fibrosis)
  • Also seen with chronic obstruction (tumour)
24
Q

What are histological characteristics of bronchiectasis?

A
  • Dilated bronchi

* Chronic suppuration

25
Q

What is tuberculosis?

A
  • Mycobacterial infection

* Chronic infection described in many body sites – lung, gut, kidneys, lymph nodes, skin

26
Q

What is the pathology of TB?

A

Pathology characterised by delayed (type IV) hypersensitivity - granulomas with necrosis

27
Q

What pathogens cause tuberculosis?

A

M. tuberculosis/M.bovis main pathogens in man

28
Q

What is a type IV hypersensitivity reaction?

A

T cell mediated hypersensitivity - formation of granulomas

29
Q

What is the pathogenicity of mycobacterium due to?

A

Due to ability:

  • to avoid phagocytosis
  • to stimulate a host T-cell response
30
Q

Describe the processes (occur together in TB) of immunity and hypersensitivity (type IV)

A
  • Immunity - T-cell response to organism enhances macrophage ability to kill mycobacteria
  • Hypersensitivity (type IV) - T-cell response causes granulomatous inflammation, tissue necrosis and scarring
31
Q

What 2 immune processes occur together in TB?

A
  • Immunity

* Hypersensitivity (type IV)

32
Q

What is primary TB?

A

1st exposure and up to 5 years afterwards

33
Q

Describe the process of a primary TB infection

A
  • inhaled organism phagocytosed and carried to hilar lymph nodes
  • Immune activation (few weeks) leads to a granulomatous response in nodes (and also in lung) usually with killing of organism
  • in a few cases infection is overwhelming and spreads
34
Q

What is secondary TB?

A

reinfection or reactivation of disease in a person with some immunity

35
Q

Does secondary TB spread?

A
  • disease tends initially to remain localised, often in apices of lung
  • however, can progress to spread by airways and/or bloodstream
36
Q

What are tissue changes in primary TB?

A
  • Small focus (Ghon focus) in periphery of mid zone of lung

* Large hilar nodes (granulomatous)

37
Q

What are tissue changes in secondary TB?

A

Fibrosing and cavitating apical lesion (cancer an important differential diagnosis)

38
Q

What is the characteristic pathology of tuberculosis?

A
  • Granulomas (macrophages, lymphocytes, large cells)

* Caseous necrosis

39
Q

How can secondary TB result in rapid death?

A

Can progress to miliary tuberculosis

40
Q

What are histological characteristics of miliary TB?

A

White foci - due to blood spread of rapidly progressing disease

41
Q

What does decreased immunity as a result of infection result in?

A

Many more organisms on acid fast stain

42
Q

Why does disease reactivate?

A
  • Decreased T-cell function (age, coincident disease (HIV), immunosuppressive therapy - steroids, cancer chemotherapy)
  • Reinfection at high dose or with more virulent organism
43
Q

What factors lead to decreased T-cell function?

A
  • age
  • coincident disease (HIV)
  • immunosuppressive therapy (steroids, cancer chemotherapy)
44
Q

What factors lead to decreased T-cell function?

A
  • age
  • coincident disease (HIV)
  • immunosuppressive therapy (steroids, cancer chemotherapy)
45
Q

What can immunocompromisation result in?

A

Virulent infection with common organism (e.g. TB)
Infection with opportunistic pathogen
* virus (cytomegalovirus - CMV)
* bacteria (Mycobacterium avium intracellulare)
* fungi (aspergillus, candida, pneumocystis)
* protozoa (cryptosporidia, toxoplasma)

46
Q

How is a diagnosis of tuberculosis confirmed?

A
  • Teamwork (physician, microbiologist, pathologist)
  • Broncho-alveolar lavage
  • Biopsy (ZN stain, etc)
47
Q

What can aspergillum infection of the immunocompromised result in?

A

Fatal haemorrhage

48
Q

Will immunocompromised individuals only be infected with one organism?

A

No, usually many organisms can be the cause of pulmonary infection

49
Q

What are the histological characteristics of a HIV-positive patient with cytomegalovirus and pulmonary oedema?

A
  • Big swollen cells

Respiratory: Pathology (4 decks)

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