Pathology of Respiratory Infections

Question 1

explain the morphological patterns and clinical context of pneumonia

Answer 1

infection involving the distal airspaces usually with inflammatory exudation (localised oedema)
fluid filled spaces lead to consolidation

Question 2

describe pathology of community acquired pneumonia

Answer 2

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

complications;
organisation (fibrous scarring)
abscess
bronchiectasis
empyema

Question 3

describe bronchopneumonia

Answer 3

infection starting in airways and spreading to adjacent alveolar lung
seen in context of pre-existing disease - COPD, cardiac failure, complication of viral infection (influenza), aspiration of gastric contents

Question 4

describe lung abscess

Answer 4

localised collection of pus
tumour-like
chronic malaise and fever
content - aspiration

Question 5

describe bronchiectasis

Answer 5

abnormal fixed dilation of the bronchi
usually due to fibrous scarring following infection (pneumonia, TB, cystic fibrosis)
seen with chronic obstruction
dilated airways accumulate purulent secretions

Question 6

describe bronchiectasis

Answer 6

abnormal fixed dilation of the bronchi
usually due to fibrous scarring following infection (pneumonia, TB, cystic fibrosis)
seen with chronic obstruction
dilated airways accumulate purulent secretions

Question 7

describe TB

Answer 7

mycobacterial infection
chronic infection described in many body sites - lung, gut, kidneys, lymph nodes, skin
pathology characterised by delayed (type IV) hypersensitivity (granulomas with necrosis)

caused by organisms - M.tuberculosis/M.bovis
others cause atypical infection especially in immunocompromised host
pathogenicity due to ability;
to avoid phagocytosis
to stimulate a host T-cell response

Question 8

describe immunity and hypersensitivty in lung infection

Answer 8

T cell response to organism enhances macrophage ability to kill mycobacteria - this ability constitutes immunity
T cell response causes granulomatous inflammation, tissue necrosis and scarring - this is hypersensitivity (type IV)
commonly both processes occur together

Question 9

describe pathology of TB - primary

Answer 9

1st exposure and up to 5 years;
inhaled organism phagocytosed and carried to hilar lymph nodes
immune activation (few weeks) leads to granulomatous response in nodes (and lung) usually with killing of organism
in few cases infection is overwhelming and spreads

tissue changes;
small focus (Ghon focus) in periphery of mid zone of lung 
large hilar nodes (granulomatous)

Question 10

describe pathology of TB - secondary

Answer 10

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 blood stream

tissue changes;
fibrosing and cavitating apical lesion (cancer an important differential diagnosis)

Question 11

describe pathology of TB - secondary

Answer 11

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 blood stream

tissue changes;
fibrosing and cavitating apical lesion (cancer an important differential diagnosis)

Question 12

describe reactivation of TB

Answer 12

due to decreased T cell function because of;
age
coincident disease (HIV)
immunosuppressive therapy (steroids, cancer chemotherapy)
reinfection at high dose or with more virulent organism

Question 13

describe the immunocompromised host

Answer 13

virulent infection with common organism 
infection with opportunistic pathogen;
virus 
bacteria
fungi
protozoa