The purpose of this study is to find out more about some of the unusual chemicals (called oligosaccharides) that can occur naturally as a result of processes in the body. Researchers want to look at how these chemicals change with time and how they change between different patients with MPSIVA. These unusual chemicals were recently discovered in the urine from patients with MPSIVA. The investigators would like to study these chemicals before a specific enzyme replacement therapy is used. If the investigators understand how these chemicals change, the investigators may be able to use them to monitor this condition in the near future as well as help doctors know whether certain therapies work well in their patients.