Idiopathic pleuritis and pleural effusion associated with birefringent material in a dog

A 21-month-old intact male Saint Bernard was examined for a two-week history of hyperpnoea. Pleural effusion was confirmed radiographically, and fluid analysis was consistent with a modified transudate. Causes of pleural effusion such as heart failure, pyothorax, hypoalbuminaemia, chylothorax, lung lobe torsion and diaphragmatic hernia were ruled out. Pleural biopsies demonstrated chronic proliferative pleuritis with the presence of birefringent particulate material within phagocytic mesothelial cells. These particles, similar to asbestos or other mineral fibres, may have played an aetiological role in the development of pleuritis and hence effusion. A positive response to corticosteroid therapy was observed. Although the dog was found dead six weeks after presentation, the disease appeared to be in clinical remission