Common Symptoms
Mucopolysaccharidosis I (MPS I) is an inherited Lysosomal Storage Disorder affecting Plotts. Affected dogs have insufficient activity of the Enzyme alpha-L-iduronidase, which is responsible for breaking down glycosaminoglycans (GAGs). GAGs are an important component of tissues throughout the body. In affected dogs there is an accumulation of breakdown products in cells causing abnormal growth and function of many different organ systems. Affected dogs typically present after 4 to 6 months of life with initial symptoms of bone and joint disease including joint laxity, delayed growth, skeletal deformities and pain on handling. Clinical signs of MPS I are most commonly associated with accumulations in the heart, bones, joints, nervous system and eyes. Other features of MPS I include cloudy eyes, arched back, stiff gait, umbilical hernia and a characteristic upturned nose. Dogs usually die due to complications of the disease or are humanely euthanized by 2-3 years of age.
Breed-Specific Information for the Plott
The Mutation of the IDUA gene associated with mucopolysaccharidosis I has been identified in the Plott, although its overall frequency in this breed is unknown.
Testing Tips
Genetic testing of the IDUA gene in Plotts will reliably determine whether a dog is a genetic Carrier of mucopolysaccharidosis I. Mucopolysaccharidosis I is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the IDUA gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Plotts that are not carriers of the mutation have no increased risk of having affected pups.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
References
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Dierenfeld AD, McEntee MF, Vogler CA, Vite CH, Chen AH, Passage M, Le S, Shah S, Jens JK, Snella EM, Kline KL, Parkes JD, Ware WA, Moran LE, Fales-Williams AJ, Wengert JA, Whitley RD, Betts DM, Boal AM, Riedesel EA, Gross W, Ellinwood NM, Dickson PI. Replacing the enzyme alpha-L-iduronidase at birth ameliorates symptoms in the brain and periphery of dogs with mucopolysaccharidosis type I. Sci Transl Med. 2010 Dec 1;2(60):60ra89.
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Menon KP, Tieu PT, Neufeld EF. Architecture of the canine IDUA gene and mutation underlying canine mucopolysaccharidosis I. Genomics. 1992 Nov; 14(3):763-8.
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Shull RM, Helman RG, Spellacy E, Constantopoulos G, Munger RJ, Neufeld EF. Morphologic and biochemical studies of canine mucopolysaccharidosis I. Am J Pathol. 1984 Mar;114(3):487-95. PubMed
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Shull RM, Munger RJ, Spellacy E, Hall CW, Constantopoulos G, Neufeld EF. Canine alpha-L-iduronidase deficiency. A model of mucopolysaccharidosis I. Am J Pathol. 1982 Nov;109(2):244-8.
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Spellacy E, Shull RM, Constantopoulos G, Neufeld EF. A canine model of human alpha-L-iduronidase deficiency. Proc Natl Acad Sci U S A. 1983 Oct;80(19):6091-5.
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