Overview Spinocerebellar Ataxia type 3 (SCA3), also known as Machado-Joseph Disease, is a rare, fatal, heriditary disease that affects the central nervous system. It is caused by a genetic defect, which means that it can only be passed on from parent to child. The defect leads to the impairment of specific nerve fibers carrying messages to and from the brain, resulting in the degeneration of the cerebellum. The symptoms vary with the age of the disease's development. The earlier the onset, the more severe the symptoms will be. SCA3 eventually destroys the physical body, but leaves the intellect intact. Therefore, affected individuals are fully aware of the symptoms which progress relentlessly until death. Death often occurs six to twenty-nine years after the disease begins developing. Currently, there is no cure for SCA3. What's in a name? spi·no·cer·e·bel·lar The term "spinocerebellar" refers to the part of the human brain affected by the disease. This area is also known as the hindbrain and consists of the cerebellum, the briain stem, and the upper part of the spinal chord. The disease shrinks and weakens the spinal chord ("spino") and cerebellum ("cerebellar"). The cerebellum is located towards the back and lower part of the head. The right side of the cerebellum controls coordination on the right side of the body, and the left side controls coordination of the left. The central part of the cerebellum is involved in coordinating very complex movements such as walking. Other parts of the cerebellum help to coordinate eye movements, speech, and swallowing. The "wasting away" of this critical area results in a loss of muscle coordination. a·tax·i·a Ataxia is a general term that means clumsiness, or loss of coordination. It is a symptom, not a specific disease. type three The number 3 represents the sequential order of discovery of SCA3 within the numerous types of SCAs. At this time, there are at least 29 different types of SCA that have been found and described. These types are given numbers (1-29) and share similarities. These numbers, however, do not imply increasing severity. Rather, SCA3 was the third type of spinocerebellar ataxia found to be linked to a chromosome and, therefore, the third gene to be identified. Ma·cha·do-Jo·seph (m-shä-d-j-sf) The name "Machado-Joseph" comes from the first families described with the symptoms of this disease in the 1970s. The families were of Portuguese/Azorean descent. This ethnic group has the highest prevalence rate of this disease though it is found worldwide. Researchers first described SCA3 in 1983 and found that MJD and SCA3 are the same disease. Link to the main page