Fucosidosis is a fatal hereditary metabolic disorder. It occurs in humans and English Springer Spaniels dogs. It is caused by insufficient activity of alpha-L-fucosidase enzyme (a lysosome enzyme). Alpha-L-fucosidase is an exoglycosidase: it cleaves out L-fucosyl residue of oligosaccharides, glycoproteins and glycolipids side-chain nonreductive ends; L-fucose (= 6-deoxy-L-galactose) and alcohol are created. If alpha-L-fucosidase does not work well, glycoconjugates (that incorporate L-fucose) are deposited in different organs (liver, heart, kidney, spleen, brain...)
In English Springer Spaniels fucosidosis expresses as a neurological disease, main symptoms are blindness, deafness, behaviour and motoric disorders, vomiting, deglutition problems... Disease manifestation starts between 18 months and 4 years. It proceeds very quickly, death comes in several weeks. Nowadays, there is no efficient therapy of fucosidosis. Fucosidosis appears in many breedings from Great Britain and Australia.
Fucosidosis in English Springer Spaniels is caused by 14th base pair deletion in fucosidase gene exon 1, causing a frame shift and formation of a premature stop codon in 152 position of enzyme.
Fucosidosis is inhered as an autosomal recessive trait. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive /negative) genotype are clinically without any symptom. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.
Genetic test uncovers disease before it is manifested. It is recommended to test all dogs before they start reproducing their selves. DNA samples can be obtained from cheek swabs (non-invasive method suitable for owners) or from blood samples taken by a veterinarian.
Thanks to Urs Giger, University of Pennsylvania School of Veterinary Medicine.
References:
Holmes NG, Acheson T, Ryder EJ, Binns MM: A PCR-based diagnostic test for fucosidosis in English springer spaniels. Vet J. 1998 Mar;155(2):113-4
Benešová E, Marková M, Lipovová P, Králová B: Fukosidasy a oligosacharidy obsahující fukosu. Chem. Listy 99, 324 - 329 (2005)
