Mucopolysaccharidosis (MPS) IIIA (dachshund type) is an inherited Lysosomal Storage Disorder affecting dogs. Affected dogs have insufficient activity of the Enzyme heparan N-sulfatase which is responsible for breaking down heparan sulfate. Heparan sulfate is an important component of tissues throughout the body. In affected dogs, there is an accumulation of breakdown products in cells, especially those of the nervous system. Affected dogs typically present around 3 years of age with neurologic deterioration.