Leukodystrophies are disorders which affect the white matter of the brain and the nervous system. Nerves are surrounded by fatty cover of a substance called myelin. In a leukodystrophy, there are problems with the growth or the development of this cover. This affects the function of the respective nerve. Myelin is made of at least ten different chemicals. Leukodystrophy is a gene defect. As a result of this defect, one of the molecules that make up myelin cannot be synthesized as it should.