Alexander disease

Alexander disease is a very rare, usually fatal genetic disorder belonging to a group of neurological conditions called leukodystrophies, in which the myelin sheath that protects nerve fibers in the brain is damaged or fails to form correctly. Most cases arise from a spontaneous, rather than inherited, mutation in the gene for glial fibrillary acidic protein on chromosome 17, and the disease follows an autosomal dominant pattern when it is passed down. Its hallmark under the microscope is the buildup of abnormal protein clumps called Rosenthal fibers inside the brain's supporting astrocyte cells, alongside destruction of white matter. The infantile form, the most common and severe, typically appears within the first two years of life with developmental delay, an enlarging head and seizures, and children with this form often do not survive past early childhood; juvenile and adult forms exist as well and tend to progress more slowly.