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Flashcards in Pathology of Lung Infection Deck (55)
1

What is pneumonia?

Inflammation of the lung - mostly due to infection but not always

2

What are the clinical features of pneumonia?

Fever and chills, unrelenting cough, sputum production (yellow or green), chest pain if pleura is inflamed, impaired gas exchange resulting in dyspnoea and tachypnoea

3

What are the three groups of pneumonia according to clinical setting?

Community acquired, hospital acquired or compromised immune host

4

What pathogen is most likely to cause community acquired pneumonia?

50% of cases are caused by streptococcus pneumoniae

5

What pathogen is most likely to cause hospital acquired pneumonia?

A gram negative bacteria

6

What pathogens are more likely in immune compromised hosts to cause pneumonia?

Fungi or protozoa (pneumocystis jirovecii)

7

What are the four ways which pathogens can reach the lung?

Inhalation of pathogens in air droplets, aspiration of infected secretions from the URT, aspirating infected particles like gastric contents or food or drink, from the blood

8

What are the three classes of pathogens causing pneumonia?

upper respiratory tract flora, enteric saprophytes, extraneous pathogens

9

What are the upper respiratory tract flora which can cause pneumonia?

Streptococcus pneumoniae, haemophilus influenzae, staphlococcus aureus

10

What are the enteric saprophytes which can cause pneumonia?

E. coli, pseudomonas

11

What are the extraneous pathogens which can cause pneumonia?

Legionella pneumophila, tuberculosis

12

What are the two patterns of infective pneumonia?

Alveolar inflammation or interstitial inflammation (atypical pneumonia)

13

What cells are involved in alveolar inflammation?

Neutrophils in the alveolar spaces (consolidation)

14

What pathogens cause alveolar inflammation?

bacterial pathogens such as streptococcus, staphylococcus, haemophilus, gram negatives

15

What are the two kinds of alveolar inflammation?

Bronchopneumonia and lobar pneumonia

16

What is the pattern of consolidation in bronchopneumonia?

Patchy and bilateral

17

What is the pattern of consolidation in lobar pneumonia?

Entirety of a single lobe

18

What does consolidation look like on a CXR?

White

19

What does consolidation look like macroscopically?

White and solid

20

What is the commonest cause of lobar pneumonia?

streptococcus pneumoniae

21

What is the commonest way to get strep pneumoniae lobar pneumonia?

community acquired

22

What are the symptoms of community acquired strep pneumoniae lobar pneumonia?

high fever with chills, raised white cell count, cough, pleuritic chest pain, blood stained sputum, gram positive diplococci present in sputum, often causes bacteraemia

23

What are the 4 stages of lobar pneumonia?

congestion, red hepatisation, grey hepatisation, resolution

24

What happens in congestion?

Protinaceous exudate full of diplococci in the alveoli

25

What happens in red hepatisation?

Consolidation with haemorrhage into airspaces

26

What happens in grey hepatisation?

mesh work of fibrin in alveolar spaces with neutrophils and macrophages

27

Which patients most commonly get bronchopneumonia?

Young and old patients or patients with chronic disease e.g. COPD, cardiac failure, malignancies or cystic fibrosis - hospitalised patients

28

What pathogens most commonly cause bronchopneumonia?

gram negative bacteria - pseudomonas or staphylococcus

29

What are the complications of pneumonia?

Pleurisy, pyothorax, empyema, abscess, bronchiecstasis, fibrosis, cysts

30

What is a lung abscess?

A cavity containing puss

31

What pathogen almost always causes lung abscess?

Staphylococcus aureus

32

What are other causes of lung abscess?

aspiration of infected contents from the URT such as gastric contents, distal to bronchial obstruction by a tumor, septic emboli to the lung

33

What cells are involved in atypical pneumonia?

Lymphocytes and macrophages in intra alveolar septa

34

What pathogens cause atypical pneumonia?

Viruses, bacteria (mycoplasma pneumonia, coxiella burnetti, legionella, chlamydia pneumoniae)

35

What is seen in the lung macroscopically in atypical pneumonia?

lung looks dark, wet and heavy - there is no consolidation

36

What is the clinical presentation of atypical pneumonia?

systemic symptoms more than respiratory systems - malaise, aches, pains, headache, diarrhoea, non productive cough - ‘walking pneumonia’

37

What does the CXR of atypical pneumonia look like?

Dots and dashes in both lung fields

38

What is tuberculosis?

a chronic granulomatous pneumonia due to infection with mycobacterium tuberculosis

39

What are the unique features of tuberculosis compared to other bacterial pneumonias?

the human body cannot eradicate it, and it can lie dormant after the initial infection before causing a secondary infection

40

What are the clinical features of primary TB?

mild often asymptomatic

41

What are the histological features of primary TB?

Ghon’s complex

42

What is a Ghon’s complex?

Ghon focus + involved hilar lymph node

43

What is a Ghon’s focus?

Granuloma (aggregate of epithelioid macrophages + multinucleate macrophages) around caseous necrosis

44

What causes the granuloma?

A type IV hypersensitivity response where monocytes under the influence of IGNgamma become epithelioid macrophages

45

How does primary TB resolve?

The immune response controls the infection and the Gohn complex heals by fibrosis, often with some calcification

46

What is secondary TB?

The reactivation of a dormant infection or a reinfection

47

What area of the lung does secondary TB effect?

Lobar pneumonia involving the upper lobe

48

What macroscopic features are seen in secondary TB?

casseous necrosis, fibrosis, calcification, cavitation (where caseation erodes into a bronchus)

49

What are the complications of secondary TB?

Spread into surrounding lung, erosion of blood vessels, erosion into bronchial tree causing spread, pleural inflammation and fibrosis, lung scarring

50

How is TB spread from person to person?

infected aerosolised droplets

51

What are the clinical features of secondary TB?

weight loss, malaise, fevers, night sweats, haemoptysis, dyspnoea and chronic cough

52

What are the features of mycobacterium tuberculosis?

aerobic rods with an acid fast wall - detected by ZN stain

53

How does TB spread around the body?

Via lymphatics to pleura or to the opposite lung, via the bronchial tree - can be coughed up into larynx and swallowed and become intestinal - or can spread via the blood stream to other organs

54

What is miliary TB?

progressive tuberculosis caused by spread through the blood stream where multiple organs are involved - macroscopically you see numerous small white granulomas in the organs

55

What is single organ TB?

Where a single organ is infected in primary TB but lies dormant and then when becomes activated has effect on only one organ e.g. Potts disease in the spine