Degenerative motor diseases refers to a group of central nervous system (CNS) disorders that have an insidious onset and lead to progressive deterioration in motor functioning. These diseases are often transmitted genetically; however, infectious agents have been linked to some conditions (e.g., spongiform encephalopathatic virus causing Cruetzfelt-Jakob disease). Not all movement disorders are progressive; in fact, Sydenham’s chorea, a condition associated with streptococcal infection and rheumatic fever, generally has a good outcome. But unlike Cruetzfelt’s, Sydenham’s is not a degenerative motor disease (DMD). Diseases in the class of DMD tend to be fatal, but only after years of slow decline. Friedreich ataxia is an example of a childhood DMD in which deterioration comes much earlier than death. In fact, death may not occur until the fifth decade of life, but confinement to a wheelchair comes a decade or two earlier. Death is often caused by medical problems associated with deteriorated physical functioning (e.g., years of immobility).