is a type of leukodystrophy. It is characterized by the destruction of white matter in the brain and abnormal protein deposits known as Rosenthal fibers. Most cases of Alexander disease begin before age 2 years (the infantile form). Symptoms of the infantile form include an enlarged brain and head, seizures, stiffness in the arms and/or legs, mental retardation, and delayed physical development. Less frequently, onset occurs later in childhood (the juvenile form) or adulthood. Common problems in juvenile and adult forms of Alexander disease include speech abnormalities, swallowing difficulties, and poor coordination. Alexander disease is caused by mutations in the GFAP gene. While this condition is inherited in an autosomal dominant fashion, most cases result from new mutations in the gene. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.