Malignant histiocytosis in three Bernese mountain dogs.

Malignant histiocytosis is a rare disease which is characterised by the neoplastic proliferation of tissue macrophages (histiocytes) leading to excessive phagocytosis of erythrocytes. The clinical signs and pathological findings in three Bernese mountain dogs are described. Two of the dogs had the same sire. The disease has been established as a familial problem in Bernese mountain dogs in other countries, although it has not been previously recorded in the United Kingdom.