Recessive Ataxias: Medical and Scientific Update.

Editors Note: Reprinted with permission of Euro-Ataxia.

Few forms of recessive ataxias have been recognized so far. The most frequent form (in Europe and in populations with European decent) is Friedreich's ataxia, which was described as early as 1863 by Nicholaus Friedreich. The second most frequent form, ataxiatelangiectasia, was not reported until 1921 and was only fully described after 1945. Other forms of recessive ataxias are much rarer and were recognized still later. These include Refsum disease, abetalipoproteinemia, ataxia with isolated vitamin E deficiency (AVED), spastic ataxia of the Charlevoix-Saguenay (RSACS or ARSACS) and infantile onset spinocerebellar ataxia (IOSCA).

Some of these rare recessive ataxias are more frequent in particular regions of the world, such as North Africa for AVED, Western Quebec for RSACS (or ARSACS) and Finland for IOSCA. This geographic patterning also allowed them to be recognized and genetically located (on a chromosome). All of them, except IOSCA, also had their gene identified during the last five years, the latest newcomer being RSACS (Engert et al. 2000). The RSACS gene is coding for a large protein of unknown function. Most Quebec patients have the same mutation and the mutation status for patients with other geographic origins is presently unknown. Due to the large size of the RSACS coding region, it is not yet clear what will be the best molecular diagnostic strategy of non-Quebec RSACS patients. Ataxia telangiectasia (AT) is in a similar situation, though the diagnosis of AT is accurately performed by biochemical tests rather than by a molecular test.

Many other forms …