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Lung- nontumor

Other non-neoplastic disease

Diffuse alveolar damage (DAD)

Reviewers: Dr. Elliot Weisenberg, M.D. (see Reviewers page)
Revised: 9 November 2011, last major update October 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

General
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● Also called adult respiratory distress syndrome, acute lung injury and noncardiogenic pulmonary edema
● Note: disease in absence of known cause is acute interstitial pneumonia (AIP)
● Rapid onset of severe, life-threatening respiratory insufficiency, cyanosis, severe arterial hypoxemia refractory to oxygen therapy; usually with severe pulmonary edema and diffuse alveolar infiltration on Xray

● Causes: sepsis, aspiration, diffuse pulmonary infections (viral, mycoplasma, Pneumocystis, tuberculosis), mechanical trauma, surfactant deficiency in newborns or near drowning; also other injury, inhaled irritants, chemical injury, radiation, amiodarone, chemotherapy, acute pancreatitis, burns or uremia

General
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● Pathophysiology: due to final common pathway of diffuse damage to alveolar capillary walls in both lungs
● Capillary defect in adults attracts white blood cells and cytokines, which further damage endothelium; may be due to endotoxin

Treatment
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● Nitric oxide (vasodilator) decreases pulmonary vascular resistance and reduces ventilation-perfusion mismatch
● Supportive care
● Aggressively treat underlying pathology if possible (infection, pancreatitis, etc.)
● Mortality now 40%, down from 60%; 190,000 cases and 75,000-80,000 deaths per year in US

Gross description
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● Heavy, firm, red and boggy lung

Gross images
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Congestive phase

Micro description
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● Congestion and hemorrhage, interstitial and intra-alveolar edema, fibrin deposition, hyaline membranes (composed of edema fluid and cellular debris), type II pneumocyte proliferation with atypia, mitotic activity, cytoplasmic hyaline bodies and intracytoplasmic lipid, intra-arterial thrombosis and bronchiolitis obliterans
● Minimal chronic inflammatory infiltrate
● May have extensive squamous metaplasia with atypia simulating squamous cell carcinoma (Hum Pathol 2002;33:1052)
● Early phase is exudative, later phase is organizing with fibrin, intra-alveolar fibrosis
● May have superimposed pneumonia

Micro images
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In immature lung

   

Hyaline membranes

Virtual slides
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Infant

Differential diagnosis
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● Pneumocystic carinii

Acute fibrinous and organizing pneumonia

General
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● May be a variant of diffuse alveolar damage (Arch Pathol Lab Med 2002;126:1064)
● Associated with collagen vascular disease, amiodarone, Haemophilus influenza, Acinetobacter, lymphoma, hairspray, construction work, coal mining, zoological work and idiopathic
● 50% mortality, 30% require mechanical ventilation
● Either death in months or subacute illness with recovery

Treatment
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● Antibiotics, steroids

Micro description
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● Dominant finding is patchy intra-alveolar fibrin, organizes into balls within alveolar spaces
● No classic hyaline membranes, no prominent eosinophils and no fibroblastic Masson bodies
● Alveolar walls have acute or chronic inflammatory infiltrate, type 2 pneumocyte hyperplasia

Micro images
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Prominent intra-alveolar fibrin

End of Lung-nontumor > Other non-neoplastic disease > Diffuse alveolar damage (DAD)

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