Alexander disease is caused by a defect in the glial fibrillary acidic protein (GFAP) gene in around 90 percent of cases, according to the Genetic and Rare Diseases Information Center. The GFAP gene is involved in the development of cell structure, but more research is needed to understand GFAP’s specific role within health and disease. It’s unknown what causes Alexander disease in the small number of other cases.
The gene defect doesn’t appear to be hereditary. Instead, it seems to occur at random. Some cases of familial Alexander disease have been reported. However, this is more often in the adult form.
According to the National Institutes of Health, only about 500 cases of Alexander disease have been reported since 1949.