Spinal chord in Hurler syndrome. Light micrograph of a section through the anterior horn of the spinal cord from a person affected by Hurler syndrome. This rare inherited disorder affects 1 in 115,000 people. It is caused by a defective enzyme that is unable to break down glycosaminoglycans (mucopolysaccharides). Glycosaminoglycans are large molecules normally found in the fluid lubricating the joints. If they are not broken down by the enzyme when entering the cells, they cause permanent cell damage that progressively hinders physical development, organ functioning and causes mental retardation. There is no known cure and individuals rarely live past the age of 10.