Histological diagnosis of mucopolysaccharidosis IIIA in a wire-haired dachshund

A four-year-old wire-haired dachshund developed progressive neurological si gns of ataxia, intention tremor and finally dysuria. Two years later, histo pathology showed that neurons throughout the brain and spinal cord were dis tended with lipopigment which was also present in macrophages. Ultrastructu rally, the pigment in the neurons occurred predominantly as electron-dense membranous whorls and stacks. There were a few vacuolated macrophages in th e meninges. Hepatocytes were highly vacuolated and electron microscopy sugg ested that they were empty membrane-bound vesicles. The disease was diagnos ed as mucopolysaccharidosis IIIA because of its similarity to other biochem ically confirmed cases in the same breed and in a New Zealand huntaway dog. Additional lesions included calcium oxalate uroliths, severe secondary cal cification of tissues including the brain and storage deposits in some neur ons, and lesions which may have been associated with high levels of the sub strate, heparan sulphate.