Leukodystrophy is a disease that involves the deterioration of white matter (myelin) in the brain. "Leuko-" means "white". "Dystrophy" refers to abnormal development.
The role of myelin is to insulate axons. An axon is part of a neuron (nerve cell). It transmits the brain's signals through the body.
When this process malfunctions, serious damage affecting the body in far-reaching ways is the result. This deterioration is called "dysmyelination".
The myelin sheath is the fatty covering for nerve fiber, which insulates the fiber. Dysmyelination hampers the healthy development of this sheath.
There are many types of leukodystrophy. Each of them stems from a genetic abnormality affecting one of the ten or more chemicals found in myelin.
Here is a summary of symptoms for some of these types.
Adrenoleukodystrophy (ALD) causes neurological decline, seizures, loss of muscle control (ataxia) and Addison's disease (impaired adrenal glands) as well as vision and hearing loss. Adrenomyelopathy is the adult form of ALD.
Alexander disease causes enlargement of the head (macrocephaly), excess fluid in the brain (hydrocephalus), seizures and dementia.
Canavan disease involves poor muscle tone, decreasing motor abilities, problems eating and mental retardation.
Cerebrotendinous xanthomatosis causes brittle bones that fracture easily as well as neurological abnormalities, ataxia and speech problems (dysarthria).
Childhood ataxia with central nervous system hypomyelination (CACH) is also known as vanishing white matter disease. Its hallmarks are neurological damage, ataxia and involuntary tightening of the muscles (spacisity).
Krabbé disease has symptoms similar to cerebral palsy. Metachromatic leukodystrophy involves dementia, muscle wasting, paralysis and vision loss.
Pelizaeus-Merzbacher disease affects mental and motor abilities. Refsum disease brings on neurological damage, and numbness, tingling and burning sensations in the extremities (peripheral neuropathy).
Most leukodystrophies are passed on genetically. Most appear in infancy or childhood though some emerge later in life.