Alexander disease is a rare genetic disorder in the family of demyelinating leukodystrophies. Its prevalence across the world is not exactly known, but has been estimated at 1 in 2,700,000 in Japan. This neurological disease is most often diagnosed in early childhood, but juvenile and adult forms also exist. Symptoms include mental retardation, epilepsy, and muscle stiffness, and their progression leads to the patient's death. It is characterised by a degeneration of the white matter and the formation of Rosenthal fibres.