ALEXANDERS-DISEASE IN A BERNESE MOUNTAIN DOG

We present a case of Alexander's disease (AD) in a Bernese mountain do g. The male dog had a clinical history of tremors of the kind legs and posterior weakness, which deteriorated rapidly to posterior paresis a nd tetraparesis. After a disease duration of 4 weeks the dog was eutha natized at 13 weeks of age. Macroscopically the brain showed moderate enlargement of the lateral ventricles. Histologically there was marked proliferation of astrocytes with abnormally large cell bodies in the white matter of the brain and the white and gray matter of the spinal cord. In these regions numerous round, club-shaped, or elongated depos its consistent with Rosenthal fibers (RFs) were found. They were most prominent in perivascular, subependymal, and subpial areas where they were perpendicularly arranged. Additionally there was considerable los s of myelin. Immunohistologically the RFs were positive for glial fibr illary acidic protein and alpha B-crystallin. Unter the electron micro scope the RFs were found to be located in the cell bodies and processe s of astrocytes and appeared as osmiophilic irregularly formed bodies of uneven size with distinct borders that were tightly associated with glial filaments. The histological, immunohistochemical, and ultrastru ctural findings of this canine case of AD are identical with those in human cases.