Pathology of Pulmonary Infections

Question 1

What bacteria is the most common bacterial cause of acute exacerbation in COPD? What type of this bacteria is it?

Answer 1

Haemophilus influenzae

Typically the non-encapsulated, non-typable forms (people are vaccinated against b capsule)

Question 2

What is the second most common cause of bacterial exacerbation of COPD? What is it morphology?

Answer 2

Moraxella catarrhalis

-> gram negative diplococci

Question 3

What are the features of pneumonia with Klebsiella and Pseudomonas?

Answer 3

Klebsiella - severe, necrotizing with thick, mucoid sputum

Pseudomonas - severe, necrotizing inflammation with vasculitis leading to thrombosis and hemorrhage

Question 4

What bacterias are commonly nosocomial?

Answer 4

Gram negatives are more commonly to be involved in nosocomials: I.e. pseudomonas or E. coli, other enteric gram negatives

S. aureus and S. pneumoniae are still feared (latter is most common in every population)

Question 5

What type of infection does aspiration pneumonia / what lung damage and why?

Answer 5

Necrotizing, fulminant infection with pulmonary abscess due to a mix of gastric acid, and aerobic / anaerobic bacteria

Question 6

What is the most frequent cause of lobar pneumonia?

Answer 6

S. pneumoniae

& other community acquired pneumonias

Question 7

What is meant by bronchopneumonia and in what type of pneumonia (broadly) does this typically occur?

Answer 7

Patchhy distribution around airways and in MULTIPLE lung lobes

Most frequent in nosocomial pneumonia

Question 8

What are the classical stages of acute bacterial pneumonia in order?

Answer 8

Congestion (hyperemia) -> red hepatization -> gray hepatization -> resolution

Question 9

What is happening in the congestion stage of pneumonia?

Answer 9

Dilated blood vessels with pulmonary edema, numerous bacteria -> not many immune cells have leaked in yet

Question 10

What is the difference between gray and red hepatization?

Answer 10

Red hepatization (firm like liver) -> happens earlier, with numerous erythrocytes, neutrophils, and fibrinous exudate

Gray -> more macrophages now as well, and RBCs have become lysed and eatin by neutrophils / MACs

Question 11

How does acute bacterial pneumonia finally resolve?

Answer 11

Enzymatic digestion of intra-alveolar exudate, with clearance by expectoration, resorption, or ingestion by dust cells

Question 12

What are some of the complications that can happen secondary to acute bacterial pneumonia?

Answer 12

1. Pleuritis
2. Pulmonary abscess - (in necrotizing infections, like S. aureus / K. pneumoniae)
3. Foci of pulmonary fibrosis
4. Bacteremia / sepsis

Question 13

What are the complications of pleuritis?

Answer 13

Exudative effusions or empyema (pus in pleural space) -> can lead to fibrous scarring with adhesions

Question 14

What are the clinical manifestations of acute bacterial pneumonia?

Answer 14

Acute onset of fever and chills

Productive cough with dyspnea and tachypnea

Left shift of WBC

Pleuritic chest pain / friction rub

Question 15

What is the most common cause of lung abscess and where does it most commonly occur?

Answer 15

Aspiration of oropharyngeal contents

-> occurs in right lower lobe (due to right broncus branching at a less acute angle)

Question 16

What patients are particularly susceptible to aspiration of oropharyngeal contents? What makes this more likely to become an abscess?

Answer 16

Impaired cough reflex -> anesthesia, unconscious, alcoholics

Abscess -> with periodontal disease, growing more anaerobes in mouth

Question 17

What condition is most likely to cause multiple pulmonary abscesses? With what bacteria?

Answer 17

Septic embolism due to IV drug user tricuspid valve endocarditis
-> most frequently S. aureus

Question 18

How can a neoplasm cause a lung abscess?

Answer 18

By obstructing a bronchial, bacteria cannot be cleared, and they form an abscess distal to the obstruction

Question 19

What type of inflammation occurs to cause lung abscess and how can this manifest on chest X-ray?

Answer 19

Suppurative inflammation -> liquefactive necrosis

Can become surrounded by fibrous connective tissue with chronicity

Chest X-ray, after airway destruction -> seen as air-fluid level (fluid sitting perfectly level in a cavity)

Question 20

What are the patient symptoms of lung abscess?

Answer 20

Fever, productive cough with foul-smelling and bloody sputum (trying to clear airway), weight loss (TNF from inflammation)

->** digital clubbing, due to growth factors released from abscess reaching systemic circulation

Question 21

What are the three major causes of atypical pneumonias?

Answer 21

Aka walking pneumonias

1. Mycoplasma pneumoniae
2. Chlamydia pneumoniae
3. Viruses (hehe i got u good)

Question 22

How do viruses predispose to bacterial pneumonia?

Answer 22

They attach to and are endocytosed by mucosal epithelial cells, and lead to cellular injury

Question 23

What viruses are known for causing bronchiolitis +/- pneumonia especially in young children?

Answer 23

RSV

human metapneumovirus

Question 24

Give two viruses which can cause atypical pneumonias, inducing cell fusion and forming inclusion bodies?

Answer 24

Rubeola virus -> measles

Varicella virus -> VZV

Question 25

Give a few other viral causes of atypical pneumonia

Answer 25

Adenovirus, rhinovirus, influenza A and B, coronavirus (usually causes URIs, but can cause SARS)

Question 26

How does atypical pneumonia appear pathologically?

Answer 26

Interstitial pneumonia - cells stay in the interstitium because lymphocytes (needed to fight viruses) cannot extravasate like neutrophils

• > mononuclear infiltrate within septae
• > occasionally complicated by alveolar damage and hyaline membrane formation

Question 27

What are the clinical symptoms / signs of atypical pneumonia?

Answer 27

Low grade fever
Dry cough (nothing in airspaces to cough up)
Mild leukocytosis (primarily lymphocytes)
Often preceded by URI

Question 28

What are the high risk populations for TB?

Answer 28

Immigrants, immunosuppressed (esp. HIV-infected), elderly / poor. patients with chronic illness, those living in crowded environments (jails, homeless shelters**)

Question 29

What is the anatomic pathology of primary TB called? What does it look like microscopically?

Answer 29

Ghon complex - in an immunocompetent individual

Necrotizing granulomatous inflammation which can progress to fibrosis and calcification, usually in mid-lung field w/ foci in hilar nodes as well

Question 30

What is secondary or postprimary TB? Where does it appear and what are the patient symptoms?

Answer 30

TB disease -> reactivation or reinfection

Appears usually in apical areas of lung

Patient will have low grade fever, night sweats, weight loss, hemoptysis, and will be infectious to other

Question 31

How does miliary TB appear? There are diseases named for where TB is spreading in the body, what is it called when it spreads to cervical lymph nodes? Vertebrae?

Answer 31

Small, scattered, gray-white foci of consolidation

Cervical lymph nodes - scrofula

Vertebrae - Pott disease

Question 32

What infection is most similar to TB and how does it appear on CXR? How large are they?

Answer 32

Histoplasmosis

• appears like coin lesion on chest X-ray
• > concentric fibrosis and calcification, with VERY tiny intracellular yeasts

-almost the same in every way to TB

Question 33

What endemic fungus is most likely to cause primary symptoms? Where does it spread to?

Answer 33

Blastomyces dermatidis

Causes fever / chills, cough, CXR shows upper lobe involvement

Most commonly spreads to skin if it disseminates (looks like skin carcinoma)

Question 34

Which endemic fungi doesn’t form granulomas?

Answer 34

I tricked you, they all do

Question 35

What is the most common opportunistic pneumonia of transplant recipients and how does it appear in pathology?

Answer 35

cytomegalovirus

Large, basophilic, intranuclear inclusion (Owl’s eye) with small, basophilic, intracytoplasmic inclusions

Question 36

What opportunistic pneumonia is common in HIV patients with CD4 <200/microL and how does it appear on histology? How is it best seen?

Answer 36

Pneumocystis jirovecii

Intraalveolar, honeycomb exudate - little ovoid cysts (crushed ping pong balls) are been seen with silver stain (think of silver middle of table in sketchy)

Question 37

What three fungi types cause pneumonia in immunocompromised patients? In what subpopulations? Give their morphology

Answer 37

1. Candida - pseudohyphae and germ tubes
2. Aspergillus - neutropenic patients, septate hyphae, 45 degree branching, invading vascular spaces (thrombosis / hemorrhage)
3. Mucormycoses - uncontrolled diabetes - 90 degree branching, aseptate

Question 38

What pneumonia is an HIV patient susceptible for at CD4+ < 50?

Answer 38

Mycobacterium avium complex

-> stains acid fast

Question 39

Who is Nocardia asteroides complex most frequently associated with? Where does it disseminate to?

Answer 39

Those with depressed cell-mediated immunity (prolonged steroid use most common, also HIV, transplant)

• > disseminates to CNS (think of the bullet going through the hat of the cowboy as he coughs)
• > disseminates to skin (think of his cow print clothes with red inflammation around them)

Question 40

Is Nocardia aerobic or anerobic? How do you treat it?

Answer 40

• > aerobic, thus causes lung infection like TB (vs Actinomyces), think of the bellows on table
• > Treat with sulfonamides (think of eggs on the table)

Question 41

What are some of the complications that can happen secondary to acute bacterial pneumonia?

Answer 41

1. Pleuritis
2. Pulmonary abscess - (in necrotizing infections, like S. aureus / K. pneumoniae)
3. Foci of pulmonary fibrosis
4. Bacteremia / sepsis