Fucosidosis is a hereditary disease that occurs when a dog has a mutation in a gene that codes for the enzyme alpha-fucosidase. This enzyme breaks down complex molecules (polysaccharides) so that they can be recycled and/or removed from a cell. The genetic mutation causes a deficiency of alpha-fucosidase; consequently, complex molecules accumulate inside the cell. This abnormal accumulation eventually interferes with the cell’s ability to function.
Most clinical signs of fucosidosis are due to abnormal storage in the cells of the peripheral and central nervous system. Some organs tolerate the accumulation of macromolecules relatively well, but the nervous system appears to be very sensitive. Clinical signs include both behavioral changes and signs of motor dysfunction that start at one to two years of age. Affected dogs exhibit bizarre behavior patterns, may be aggressive or unusually depressed, and appear to forget previously learned behaviors. An affected dog may resist restraint and appear unsteady on its feet. The dog may also appear blind and deaf and may suffer from gastrointestinal disorders such as dysphagia, regurgitation, and diarrhea. Unlike PFK deficiency, this disease progresses rapidly, and death or euthanasia usually occurs within a few weeks from the onset of clinical signs.
Fucosidosis is inherited as an autosomal recessive trait in show and field English Springer Spaniels. A dog that receives a copy of the mutant gene from both parents will show clinical signs. A dog with one copy of the defective gene is a carrier; it will appear healthy but will pass the mutation to its offspring. Researchers at the University of Pennsylvania have developed a test to detect the deletion that occurs in the gene that codes for alpha-fucosidase. This test can detect whether a dog is affected or is a carrier.
Currently, the disease is most prevalent in the conformation lines in the United Kingdom and Australia. However, cases have also been described in field trial dogs. In the United States, clinical cases have been identified, but the number of carriers is still unknown. Fucosidosis may be an emergent disease in the United States, and breeders should consider screening their animals for the presence of carriers. Any English Springer Spaniel that exhibits multifocal neurological signs, especially a dog descended from English families, should be tested for fucosidosis.
Like PFK deficiency, fucosidosis testing requires a DNA sample. The same sample obtained for PFK screening may also be used for fucosidosis. For information on submitting a sample, contact
Dr. Urs Giger/PFK Deficiency
Veterinary Hospital, Room 4006
University of Pennsylvania
3900 Delancy Street
Philadelphia, PA 19104-6010
Information provided courtesy of Dr. Urs Giger.