Leukodystrophy, any of the central nervous system diseases involving demyelination of parts of the white matter of the brain, is relatively rare, reports RightDiagnosis. The most common of these diseases, Canavan disease, occurs in approximately one in 6,400 people in the United States.
Adrenoleukodystrophy, the second most common type of leukodystrophy, occurs in approximately one in 20,000 people in the United States, according to RightDiagnosis. Some types of leukodystrophy are reported simply as "rare," meaning they occur in less than one in 200,000 people. These rare types are Alexander disease, Alexander syndrome, Krabbé disease and Pelizaeus-Merzbacher disease. No information is available from RightDiagnosis about the frequency of Refsum disease or metachromatic leukodystrophy.