Acute Fibrinous and Organizing Pneumonia

Definition

Shares acute/subacute onset of symptoms with AIP/DAD
- Age of onset 33-78
Patchy involvement rather than diffuse
- Intervening lung is normal
Alveoli are filled with balls of fibrin
- No hyaline membranes
Organization present in all cases
Mild to moderate interstitial lympho-plasmacytic interstitial infiltrate
Reactive pneumocyte hyperplasia
Vascular thrombi in some cases
Rapid progression in about half of patients with resultant death, similar to AIP
Has been proposed as a variant of AIP/DAD
Only one series (Beasley 2002) and a few case reports

Gerald J Berry MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342