page_title: Leukodystrophy
section_title: Epidemiology
hierarchical_section_title: Leukodystrophy / Epidemiology
caption_attribution_description: Illustration from Anatomy &amp; Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013.
context_page_description: Leukodystrophies are a group of usually inherited disorders characterized by degeneration of the white matter in the brain. The word leukodystrophy comes from the Greek roots leuko, "white", dys, "abnormal" and troph, "growth". The leukodystrophies are caused by imperfect growth or development of the myelin sheath, the fatty insulating covering around nerve fibers. Leukodystrophies may be classified as hypomyelinating or demyelinating diseases, depending on whether the damage is present before birth or occurs after. Other demyelinating diseases are usually not congenital and have a toxic or autoimmune cause.
  When damage occurs to white matter, immune responses can lead to inflammation in the central nervous system, along with loss of myelin. The degeneration of white matter can be seen in an MRI scan and used to diagnose leukodystrophy. Leukodystrophy is characterized by specific symptoms including decreased motor function, muscle rigidity, and eventual degeneration of sight and hearing. While the disease is fatal, the age of onset is a key factor, as infants have a typical life expectancy of 2–8 years, while adults typically live more than a decade after onset.
context_section_description: Currently, no research has shown a higher prevalence of most leukodsytrophy types in any one place around the world. There is, however, a higher prevalence of the Canavan disease in the Jewish population. 1 in 40 individuals of Ashkenazi Jewish descent are carriers of Canavan disease. This estimates to roughly 2.5%. Additionally, due to an autosomal recessive inheritance patterns, there is no significant difference found between affected males and affected females for most types of leukodystrophy including, but not limited to, metachromatic leukodystrophy, Krabbe disease, Canavan disease, and Alexander disease. The one exception to this is any type of leukodystrophy carried on a sex chromosome, such as X-linked adrenoleukodystrophy, which is carried on the X-chromosome. Because of the inheritance pattern of X-linked diseases, males are more often affected by this type of leukodystrophy, although female carriers are often symptomatic, though not as severely so as males. To date, there have been no found cases of a leukodystrophy carried on the Y chromosome.
caption: X-linked Recessive Inheritance
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