(aka Hamman-Rich syndrome)

Epidemiology

• Mean Age of Onset: 50’s (Range: 7-83 y/o)
• Rare fulminant form of acute onset lung injury (ALI)
• Usually occurs in a previously healthy individual
• Probably represents what Hamman and Rich described as Acute Diffuse Interstitial Fibrosis (Hamman-Rich Syndrome)
• Relationship to Smoking: unknown
• Sex: no sex predilection
• Prodrome: prodromal illness lasting 7-14 days is common

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Etiology

• Unknown

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Physiology

• [[Diffuse Alveolar Damage]] -> [[Acute Lung Injury-ARDS]], and/or [[Diffuse Alveolar Hemorrhage]]
  • Exudation of serum proteins and RBC into alveolar spaces
  • Necrotic, sloughed alveolar epithelium
  • Edematous interstitium
  • Hyaline membranes (eosinophilic debris consisting of necrotic epithelial cells, protein, and fibrin) form within alveoli
• Reparative/Organizing Phase:
• Irreversible Fibrosis/Honeycombing: may occur with protracted or repeated injury

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Pathology

• Diffuse Alveolar Damage
• Pathologic Features:
  • Temporal Appearance: uniform
  • Interstitial Inflammation: scant
  • Collagen Fibrosis: none
  • Fibroblast Proliferation: diffuse
  • Microscopic Honeycombing: none
  • Intra-Alveolar Macrophage Accumulation: none
  • Hyaline Membranes: occasional, focal

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Diagnosis

• FOB:
• ABG: hypoxemia
• OLB: usually required for diagnosis
• CXR/Chest CT Patterns:
  • Diffuse Bilateral Airspace Opacification (similar to ARDS): may be predominantly subpleural in location
    • Bilateral, Patchy, Symmetric Ground-Glass:
    • Bilateral Airspace Consolidation: may be seen
    • Mild Honeycombing (Usually <10%): may occur
• CBC: not helpful in diagnosis

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Clinical

• Interstitial Pulmonary Fibrosis (see [[ILD-Etiology]])
  • Acute onset: symptoms may progress over days-weeks
  • Dyspnea:
  • Fever:
  • Cough:
• Acute Lung-ARDS (see [[Diffuse Alveolar Damage]], [[Acute Lung Injury-ARDS]], and [[Diffuse Alveolar Hemorrhage]]

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Treatment

• Poor response to steroids (62% mortality rate)

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Prognosis

• Mortality Rate: 62%
• Most patients die within 3 months of presentation
• Complete recovery is possible though (unlike UIP)
• In those that recover, substantial recovery of lung function occurs
• Some survivors manifest recurrences and chronic, progressive ILD

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References

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