Early-onset (infantile) Alexander disease is associated with mutations in the glial fibrillary acidic protein (GFAP) gene and two hot spots correlate to the severe phenotype. No molecular mechanisms have been elucidated in late-onset (juvenile) Alexander disease. The authors report a novel GFAP mutation in a patient with juvenile Alexander disease. The authors discuss similar molecular mechanisms in another intermediate filament disease and propose a possible molecular pathogenesis in juvenile Alexander disease.