Mucopolysaccharidosis I in domestic shorthaired cats

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease characterized by intracellular accumulation of glycosaminoglycans dermatan and heparan sulfates. Affected cats are deficient in the lysosomal enzyme alpha-L-iduronidase, which is part of the glycosaminoglycan degradation pathway. The disease is manifested by flat and broad cheeks, a large head with small ears, thickened neck skin, broad cervical vertebrae and hip subluxation. Other symptoms include an abnormal gait, corneal opacity and a heart murmur due to mitral insufficiency may occur.

The causative mutation is a 3 bp deletion (c.1042_1044del) in the IDUA gene encoding alpha-L-iduronidase.

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

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected kittens.

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References:

He, X.X., Li, C.M., Simonaro, C.M., Wan, Q., Haskins, M.E., Desnick, R.J., Schuchman, E.H. : Identification and characterization of the molecular lesion causing mucopolysaccharidosis type I in cats Molecular Genetics and Metabolism 67:106-112, 1999. Pubmed reference: 10356309