Pathology of Pulmonary Infections Flashcards

1
Q

How can pneumonia be classified?

A
By clinical setting (e.g. community acquired pneumonia)
By organism (mycoplasma, pneumococcal etc)
By morphology (lobar pneumonia, bronchopneumonia)
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2
Q

What is pneumonia?

A

Infection involving the distal airspaces usually with inflammatory exudation/localised oedema
Fluid filled spaces lead to consolidation

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3
Q

Describe the 4 steps of pneumonia?

A
  • Exudation of fibrin-rich fluid
  • Neutrophil infiltration
  • Macrophage infiltration
  • Resolution
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4
Q

What is lobar pneumonia?

A

Confluent consolidation involving a complete lung lobe which is most often due to Streptococcus pneumoniae (pneumococcus).
Can be seen with other organisms (Klebsiella, Legionella)

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5
Q

What is Bronchopneumonia? Which organisms cause it?

A

Infection starting in airways and spreading to adjacent alveolar lung.
Most often seen in the context of pre-existing disease.

Strep. Pneumoniae, Haemophilus influenza, Staphylococcus, anaerobes, coliforms

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6
Q

What is Bronchiectasis?

A

abnormal fixed dilatation of the bronchi, usually due to fibrous scarring following infection - complication of pneumonia

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7
Q

What is Tuberculosis?

A

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

characterised by delayed type IV hypersensitivity (granulomatous)

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8
Q

What are the main pathogens in TB?

A

M. tuberculosis

M.bovis

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9
Q

Describe how immunity and hypersensitivity occur in TB?

A

Immunity = T-cell response to organism enhances macrophage ability to kill mycobacteria

Hypersensitivity = T-cell response causes granulomatous inflammation, tissue necrosis and scarring

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10
Q

Describe the pathology of primary TB - first exposure?

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
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11
Q

Describe the pathology of secondary TB - second exposure?

A

reinfection or reactivation of disease in a person with some immunity, disease tends initially to remain localised, often in apices of lung.
Can progress to spread by airways and/or bloodstream

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12
Q

How is TB diagnosed?

A

broncho-alveolar lavage

biopsy

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13
Q

Why would TB reactivate?

A
decreased T-cell function
age
coincident disease (HIV)
immunosuppressive therapy (steroids, cancer chemotherapy)
reinfection at high dose or with more virulent organism
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