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Alexander`s disease, a neurodegenerative disorder, was identified in 1949 on the basis of neurohistological criteria, i.e., the presence of dystrophic astrocytes containing intermediate filament aggregates (Rosenthal fibers) associated with myelin abnormalities. Since then, different clinical forms have been individualized. The infantile form (birth to 2 years), the most common, is characterized by its early onset and severe evolution. Its symptomatology associates progressive megalencephaly (sometimes hydrocephaly), retarded psychomotor development or mental deterioration, pyramidal signs, ataxia and convulsive seizures. Computed tomography scan and magnetic resonance imaging suggest the diagnosis by revealing white matter anomalies, predominantly in the frontal lobes. Juvenile forms start in school-aged children and associate spastic paraplegia and progressive bulbar signs. Adult forms are heterogeneous and difficult to diagnose. This rare disease, often considered to be a leukodystrophy, is usually sporadic; only a few familial cases have been reported. The discovery of Rosenthal fibers in transgenic mice overexpressing human glial fibrillary acidic protein (GFAP), which is the main intermediate filament of astrocyte, led to the search for mutations in its encoding gene. More than 20 GFAP mutations have been reported; they are de novo dominant mutations. However, a prenatal diagnosis seems desirable in light of the risk of germinal/germ-cell mosaicism. At present, treatment is purely symptomatic. |