3- pathology of respiratory tract

Question 1

what is pneumonia?

Answer 1

• infection of long parenchyma (functional tissue of an organ)
• infection involving distal airspaces, usually with inflammatory exudation (localised oedema)

Question 2

what are the classifications of pneumonia by morphology?

Answer 2

• lobar pneumonia (whole lobes)
• bronchopneumonia (bits of lobes)

Question 3

what are the classifications of pneumonia by clinical setting?

Answer 3

• community
• hospital

= either where infection acquired or how/why patient acquired it - again, doesn’t necessarily tell you what but helps narrow done list

Question 4

what are the classification of pneumonia by organisms?

Answer 4

stupid question soz - just saying that definitive classification is by what organism caused it = specific treatment can be made

Question 5

what is lobar pneumonia?

Answer 5

= confluent consolidation involving most/all of lung lobe

• Consolidation is when lung tissue solidified because of accumulation of inflammatory cells, fluid, and debris in alveoli
• areas of consolidation within a lobe merge together to form larger, continuous patches of affected lung tissue

Question 6

what organisms is most common cause of lobar pneumonia?

Answer 6

strep pneumoniae

(usually community acquired in healthy, younger adult)

Question 7

what are some less common organisms that can also cause lobar pneumonia?

Answer 7

• Klebsiella pneumoniae - commonly in debilitated or malnourished adults – DM, alcoholics
• Legionella pneumophila – individuals with co-morbidities – heart, renal, haematological disease, immunosuppressed, transplant patients

Question 8

what is bronchopneumonia?

Answer 8

• infection starts in terminal airways and spreads adjacent to alveolar lung
  
  • widespread, patchy
  • often bilateral, basal

Question 9

what organisms cause bronchopneumonia?

Answer 9

wide variety = strep pneumoniae, haemophilus influenza, staphylococcus, anaerobes, coliforms

Question 10

what may help narrow down wide variety of organisms that can cause bronchopneumonia?

Answer 10

clinical context may help e.g. staph/anaerobes/coliforms seen in aspiration

Question 11

when is bronchopneumonia mostly seen in?

Answer 11

most seen in context of pre-existing disease:
- COPD
- Cardiac failure (elderly)
- Complication of viral infection (influenza)
- Aspiration of gastric contents

Question 12

what is differences in appearance of microscopy in pneumonia stages?

Answer 12

• normally, the alveoli look like big white spaces with thin walls
• during acute period, alveoli filled with neutrophils
• as infection progresses exudate(mostly made of neutrophils but also macrophages, fibrin) within alveoli begins to organise
• exudate becomes formed masses of macrophage & fibroblasts.

= this can either be broken down by enzymes or reabsorbed by phagocytes by macrophages (resolution) or undergo fibrosis (scarring)

Question 13

what are complications of pneumonia?

Answer 13

• fibrous scarring
• abscess
• empyema
• bronchiectasis

Question 14

what is a lung abscess?

Answer 14

Localised collection of pus → leads to necrosis of involved lung parenchyma

Question 15

when do lung abscess mostly occur?

Answer 15

• Most result as a complication of aspiration = foreign material, such as food, liquids, or vomit, is inhaled into the lungs instead of being swallowed into the digestive system →in that case mixed infections so Mixed organisms causing abscess
• Can occur after any bacterial pneumonia

Question 16

what is empeyema?

Answer 16

• collection of pus in pleural cavity
• can organise leading to fibrous adhesions within pleural cavity

Question 17

what is bronchiectasis?

Answer 17

• abnormal fixed dilation of bronchi & bronchioles usually due to fibrous scarring following infection (pneumonia, TB, cystic fibrosis) or with tumour
• the dilated airways accumulate purulent secretion and that makes sort of cycle of infection

Question 18

what is tuberculosis?

Answer 18

chronic pulmonary & systemic disease
- primary infection occurs in lung then chronic infection in many sites (lung, gut, kidneys, lymph nodes, skin)

Question 19

what is cause of tuberculosis?

Answer 19

mycobacterial infection, commonly:
- Mycobacterium tuberculosis (most common)
- Mycobacterium bovis – infection seen in places with infected dairy cows and no routine pasteurisation of milk (not really seen in scotland)

• Other mycobacteria cause atypical infection especially in immunocompromised host

Question 20

what helps the pathogenicity of mycobacterium?

Answer 20

• ability to avoid phagocytosis
• ability to stimulate host T cell response

Question 21

what characterises the pathology of tuberculosis?

Answer 21

• delayed (type IV) hypersensitivity reaction
• granulomatous inflammation which necrosis

= T cell response to organism enhances macrophage ability to kill mycobacteria & T cell response causes granulomatous inflammation, tissue necrosis & scarring

Question 22

what is primary TB?

Answer 22

what happens in first exposure and up to 5 years afterward

• Inhaled organism phagocytosed and carried to hilar lymph nodes
• Immune activation (few weeks) leads to a granulomatous response in nodes (and in lung) usually leading to killing of organism

*can lead to progressive disease but not very common (5%)

Question 23

what is secondary TB?

Answer 23

• 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

Question 24

why does TB re-activate/re-occur?

Answer 24

you get re-infected as host defences lowered like decreased T cell function (age, coincident disease causing immunocompromised (e.g. HIV), immunosuppressive therapy (steroids, cancer chemotherapy))

Question 25

usually, where is primary TB?

Answer 25

near pleura, lower part of upper lobe or upper part of lower lobe

Question 26

what is ghon focus and ghon complex?

Answer 26

• both aspects of primary TB

ghon focus = focused areas of consolidation in lung
ghon complex = ghon focus + enlarged hilar nodes (granulomatous inflammation

Question 27

what happens to tissues in secondary TB?

Answer 27

fibrosing (scarring + fibrosis) and cavitating apical lesion (lesion that has hollow space in it due to necrosis)

Question 28

what is the final stage/most severe form of tuberculosis?

Answer 28

= haematogenous (bacteria travels through blood stream to infect different sites of body)
- disseminated TB = miliary TB due to looking like millet seeds - seed like lesions scattered (tiny granulomas)

Question 29

what is key characteristic of tuberculosis under microscope?

Answer 29

granulomas with caseous necrosis centre

granuloma = aggregate of epithelioid macrophages

*caseous necrosis = think TB

Question 30

what stain can be used for testing TB?

Answer 30

Ziehl Neelsen (ZN) stain = highlights mycobacteria (small rod shaped organisms staining purple)

stain because alcohol acid fast bacilli = something in cell wall that highlights (called alcohol fast because unlike lots of other organisms retain dye even after alcohol & acid)

Question 31

what is difference in microscopy for people who are immunocompromised in TB?

Answer 31

can see way more of the purple rods than in normal people with ZN stain

(alveolar spaces also filled with amorphous debris in TB)

Question 32

what are common pathogens that affect immunocompromised people
a) virus
b) bacteria
c) funghi
d) protozoa

Answer 32

• virus (cytomegalovirus, herpesvirus)
• bacteria (Mycobacterium avium intracellulare)
• fungi (aspergillus, candida, pneumocystis, cryptococcus)
• protozoa (cryptosporidia, toxoplasma)

Question 33

what is different about symptoms in immunocompromised people?

Answer 33

muted signs or symptoms or completely different ones = High index of suspicion required for diagnosis

Question 34

what is involved in diagnosis of TB in immunocompromised?

Answer 34

• High index of suspicion
• Multidisciplinary (physician, radiologist, microbiologist, pathologist)
• Broncho-alveolar lavage (BAL) = flushing out airways to try and collect cells & mucus etc
• Cytology/biopsy (with lots of special stains)

Question 35

what is special stain for pneumocystitis jiroveci?

Answer 35

grocott = stains black when positive