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 glial cells which produce the myelin sheath, the fatty insulating covering around nerve fibers. Leukodystrophies may be classified as hypomyelinating or demyelinating diseases, respectively, depending on whether the damage is present before birth or occurs after. While all leukodystrophies are the result of genetic mutations, other demyelinating disorders have an autoimmune, infectious, or metabolic etiology. When damage occurs to white matter, subsequent immune responses can lead to inflammation in the central nervous system (CNS), along with the loss of myelin. The degeneration of white matter can be seen in an MRI scan and is 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. Treatment options are limited, although hematopoietic stem cell transplantations using bone marrow or cord blood seem to help in certain leukodystrophy types, while further research is being done.

Muscular dystrophies (MD) are a genetically and clinically heterogeneous group of rare neuromuscular diseases that cause progressive weakness and breakdown of skeletal muscles over time. The disorders differ as to which muscles are primarily affected, the degree of weakness, how fast they worsen, and when symptoms begin. Some types are also associated with problems in other organs.