Acute fibrinous and organizing pneumonia in a dog, and brief literature review.

In domestic species, the characterization and categorization of interstitial pneumonias have been limited, and non-infectious causes of such diseases are reported infrequently. A 6-y-old, castrated male French Bulldog with a history of brachycephalic obstructive airway syndrome and chronic regurgitation was evaluated because of respiratory distress. The dog was diagnosed antemortem with a heart-base mass and right-sided congestive heart failure via trans-thoracic echocardiography; euthanasia was elected, followed by postmortem examination. Gross findings included a large heart-base mass and diffusely dark-purple, firm, and heavy lungs, with the greatest severity in the caudal lung lobes. Histology findings confirmed that the heart mass was a chemodectoma. Lung was consolidated by organizing fibrin aggregates in alveoli, as well as organizing polypoid aggregates of fibrin and/or variably mature connective tissue partially or completely filling and obscuring bronchioles and alveolar ducts, findings consistent with acute fibrinous and organizing pneumonia (AFOP). AFOP, a debilitating condition with a wide variety of underlying causes, has features similar to, yet distinct from, other interstitial lung diseases, including diffuse alveolar damage and organizing pneumonia. AFOP is rarely and only recently reported in humans, and, to our knowledge, has not been reported previously in a dog.