L32 Infectious Lung Disease and Diffuse Alveolar Damage

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jknell
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202577
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L32 Infectious Lung Disease and Diffuse Alveolar Damage
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2013-02-22 13:54:07
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Pulmonary II
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Pulmonary II
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  1. Community Acquired Pneumonia
    • -Most are bacterial
    • -May follow viral URI
    • -Usually abrupt onset

    • Symptoms:
    • -high fever
    • -chills
    • -pleuritic chest pain
    • -productive mucopurulent cough
    • -+/- hemoptysis

    • BACTERIAL
    • 1. Strep pneumo
    • -underlying chronic disease
    • -congenital or acquired Ig deficiencies
    • -decreased spleen function
    • 2. H. flu
    • 3. Moraxella
    • 4. S. aureus
    • 5. Klebsiella
    • 6. Legionella
  2. Community Acquired Pneumonia Pathology
    Intra-alveolar Pneumonia

    • Two gross patterns:
    • 1. Lobar Pneumonia
    • 2. Bronchopneumonia
    • -can turn into lobar pneumonia

    • *patterns frequently overlap
  3. Lobar Pneumonia
    • -large portion of or complete lobe involved
    • -typical pattern fro S. pneumo

    • Four Stages:
    • 1. Congestion
    • 2. Red hepatization
    • 3. Gray hepatization
    • 4. Resolution
  4. Lobar Pneumonia: Congestion
    -24 hours

    • Gross:
    • -heavy, boggy and red

    • Histology:
    • -vascular congestion
    • -intra-alveolar fluid
    • -few neutrophils
    • -numerous bacteria
  5. Lobar Pneumonia: Red Hepatization
    -several days

    • Gross:
    • -red, firm, dry and airless
    • -liver like consistency

    • Histology:
    • -alveoli filled with exudate of blood cells, NPs, fibrin
  6. Lobar Pneumonia: Gray Hepatization
    -occurs after several days, lasts a few days

    • Gross:
    • -gray-brown, dry surface

    • Histology:
    • -RBCs disintegrate
    • -accumulation of fibrin
    • -persistence of some PMNs
    • -necrotic debris
  7. Lobar Pneumonia: Resolution
    -occurs at 8-10 days

    • Gross:
    • -may return to normal
    • -may have areas of fibrous thickening or pleural adhesions

    • Histology:
    • 1. Exudate digested and cleared
    • 2. Organizing pneumonia
    • -fibroblasts heal
  8. Bronchopneumonia
    • -patchy distribution
    • -may be in one lobe, more frequently multilobar
    • -ca be bilateral and basally located

    *common pattern from H. flu and Legionella

    • Gross:
    • -well developed lesions
    • -3-4cm
    • -gray-red yellow

    • Histology:
    • -NP rich exudate fills bronchi, bronchioles, alveoli
    • -large intervening areas that are normal
  9. Community Acquired Atypical Pneumonia
    • Atypical because:
    • -moderate amounts of sputum production
    • -no physical findings of consolidation
    • -only moderate elevation of white cell count
    • -lack of alveolar exudate

    • Organisms:
    • -Mycoplasma pneumoniae
    • -Viruses (Influenza, RSV, adenovirus, rhinovirus, rubeola, varicella)
    • *Typically need cells to replicate
  10. Influenza Virus
    • -Orthomyxoviridae
    • -Influenza A and B/Influenza C
    • -Natural reservoir is waterfall (usually asx, shed virus in fecal material)

    • Integral Membrane Proteins
    • 1. HA (hemagglutinin)
    • 2. NA (neuraminidase)
    • 3. M2
    • *many subtypes of HA and NA

    • Antigenic Drift
    • -mutations within a single subtype of HA or NA
    • -causes epidemics

    • Antigenic Shift
    • -reassortment of the segments of the viral genome
    • -causes pandemics
  11. Interstitial Pneumonia
    • Pathophysiology:
    • -organism attaches to respiratory epithelium
    • -followed by necrosis of cells and inflammatory response
    • -fluid may leak into alveolar spaces and mimic bacterial pneumonia
    • -predisposes to secondary bacterial infections (damage to epithelium inhibits mucociliary clearance)

    • Gross:
    • -may be patchy or involve whole lobes
    • -affected areas are red-blue, congested and sub-crepitant

    • Histology:
    • -alveolar septae are widened
    • -mononuclear infiltrate of lymphocytes, histiocytes and plasma cells (vs. PMNs)
    • -alveoli may be free of exudate but sometimes may contain proteinaceous material as seen in ARDS
  12. Aspiration Pneumonia
    • 1. Aspiration of infective material
    • -teeth
    • -oral surgery

    • 2. Aspiration of gastric contents
    • -usually organisms from oral pharynx

    Leads to a pneumonia that is partially chemical (gastric acid) and partially bacterial (oral pharynx flora)

    • Organisms:
    • -anaerobic (bacteroides, prevotella, fusobacterium, peptostreptococcus)
    • -aerobic (S. pneumo, S. aureus, H. flu, Pseudomonas)

    • Position:
    • -upright --> R middle and lower lung
    • -recumbent --> right upper lobe

    *often necrotizing pneumonia and may lead to abscess formation
  13. Lung Abscesses
    -localized area of suppurative necrosis within the pulmonary parenchyma resulting in the formation of large cavities

    -Necrotizing pneumonia has similar process resulting in multiple small caviations (can evolve into abscess)

    • Organisms:
    • -anaerobic oral organisms (prevotella, bacteroides, fusobacterium, peptostreptococcus)
    • -aerobic and anaerobic streptococci, S. aureus, GN organisms

    • Causes:
    • 1. Aspiration
    • 2. Complication of necrotizing bacterial pneumonias
    • 3. Bronchial obstruction (carcinomas)
    • 4. Septic Emboli (endocarditis of R heart)
    • 5. Hematogenous spread of bacteria (staphylococcal bacteremia)

    • Acute:
    • -cavity contains pus
    • -walled off by fibrin, leukocytes, granulation tissue

    • Chronic:
    • -cavitary lesion surrounded by thick fibrous wall
  14. Chronic Pneumonia
    -most often localized lesion in an immunocompetent person

    • Organisms:
    • -Mycobacterium tuberculosis
    • -Fungi
  15. Tuberculosis
    • -rod shaped bacteria
    • -acid fast (mycolic acid)

    • Stages:
    • 1. Primary
    • -previously unexposed person
    • -usually asx
    • -lower part of upper lobe or upper part of lower lobe
    • -Ghon complex

    • 2. Secondary
    • -previously exposed person
    • -occurs when host defenses are weakened
    • -sx: fever, night sweats, hemoptysis, pleuritic chest pain
    • -caseating granulomas in apices

    • 3. Miliary
    • -either primary or secondary
    • -due to lympathic or hematogenous spread
    • -many 1-2mm granulomas throughout lungs and other organs

    • Histology:
    • -caseating and non-caseating granulomas surrounded by histiocytes and Langerhans-type giant cells
  16. Bronchiectasis
    • -permanent dilatation of bronchi and bronchioles
    • -caused by destruction of the muscle and elastic tissue
    • -from or associated with chronic necrotizing infections
    • -associated with CF, immunodeficiency, PCD, post-infection, obstruction

    • Sx:
    • -severe persistent, productive cough
    • -foul-smelling sometimes bloody sputum
    • -dyspnea
    • -orthopnea

    • Pathogenesis:
    • -obstruction and/or infection of airway leading to inflammation and damage of walls --> fibrosis

    • Histology:
    • -NPs and lymphocytes in the airway walls
    • -ulcerations of mucosa may occur
    • -fibrosis in chronic cases
  17. Diffuse Alveolar Damage
    -correlates clinically with ARDS

    • Etiology:
    • -infection/sepsis/shock
    • -inhalants (O2 toxicity/smoke)
    • -drugs
    • -radiation
    • -hematologic disorders (DIC, TRALI)
    • -idiopathic

    Onset: rapid (24-48h)

    • Three Phases:
    • 1. Exudative (acute)
    • 2. Proliferative (organizing)
    • 3. Fibrotic (chronic) *may or may not occur

  18. Exudative Stage
    • Gross:
    • -Early: congestion, edema
    • -Non-crepitant
    • -dark red to blue

    • Histology:
    • -edema due to injury of type I pneumocytes and endothelial cells
    • -hyaline membranes (precipitated plasma prots and cytoplasmic/nuclear debris from sloughed epithelial cells)
  19. Proliferative Stage
    • Gross:
    • -non-crepitant, rubbery, firm
    • -patchy red-brown, yellow gray

    • Histology:
    • -exudate beginning to organize: fibroblasts and myofibroblasts proliferate --> granulation tissue
    • -type II pneumocyte hyperplasia
  20. Fibrotic Stage
    • -occurs in patients who survive in 3-4 weeks
    • -usually on a ventilator

    • Gross:
    • -spongy, cystic, pale gray

    • Histology:
    • -dense fibrotic tissue
    • -squamous metaplasia

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