We recently began the Alexander Disease Biomarker Study. The purpose of this study is to learn more about Alexander disease and the changes in a gene and a protein called GFAP. The GFAP gene directs the production of a particular protein, also called GFAP, which stands for "glial fibrillary acidic protein". This protein is altered in patients with Alexander disease, a rare disease that mostly affects young children. The disease affects the brain and spinal cord, often causing seizures and delayed development. One third of all patients with Alexander disease seem to experience their first symptoms much later (such as difficulties with swallowing or walking), as adolescents or adults. We are interested in finding better ways of measuring the severity of this disease, and whether changes in other genes or proteins also affect Alexander disease.