Mucopolysaccharidosis I in the Plott Hounds

Mucopolysaccharidosis I is a lysosomal storage disease in which mucopolysaccharides (glycosaminoglycans – dermatan, heparan, and chondroitin sulfate) accumulate in the lysosomes of various tissues. Clinical signs include stunted growth, joint problems, progressive lameness, and visual impairment caused by corneal clouding.

In the Plott Hound breed, the disease is caused by a c.155+1G>A mutation in the IDUA gene, which encodes the enzyme alpha-L-iduronidase, which plays a key role in the breakdown of glycosaminoglycans.

The mutation is inherited in an autosomal recessive manner. This means that the disease only develops in individuals who inherit the mutated gene from both parents. Carriers of the mutated gene are clinically healthy, but they pass the mutation on to their offspring. In the case of mating two heterozygous individuals, theoretically 25% of offspring will be completely healthy, 50% will be carriers, and 25% will inherit the mutated gene from both parents and will therefore be affected by the disease.

Genetic testing can clearly reveal an animal's genotype and is a useful tool for breeders to prevent the unintentional breeding of affected puppies.

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References:

Menon, K.P., Tieu, P.T., Neufeld, E.F. : Architecture of the Canine IDUA Gene and Mutation Underlying Canine Mucopolysaccharidosis-I Genomics 14:763-768, 1992. Pubmed reference: 1339393.