The complex clinical and genetic classification of inherited ataxias. II. Autosomal recessive ataxias

Autosomal recessive ataxias are a heterogeneous group of rare neurodegenera tive diseases characterized by early onset cerebellar ataxia associated wit h various neurologic, ophthalmologic and systemic signs. In comparison with autosomal dominant ataxias, the group of recessive ataxias is less extensi vely characterized. In fact, only a few conditions have been genetically ch aracterized. The pathogenesis of these forms is associated with a "loss of function" of specific cellular proteins involved in metabolic homeostasis, cell cycle, and DNA repair/protection processing. The two most common autos omal recessive ataxias, in European countries, are Friedreich's ataxia and ataxia telangiectasia. Other forms are much less frequent, and include atax ia with vitamin E deficiency, abetalipoproteinemia, Refsum's disease, spast ic ataxia, infantile onset spinocerebellar ataxia, and ataxia with oculomot or apraxia. These pathological conditions, although extremely rare, have ne vertheless to be carefully considered in differential diagnosis, not only f or correct nosographical. classification, but particularly, for specific pr ognostic and therapeutic implications. Some of these diseases exhibit a pec uliar regional distribution. An updated review of the clinical, genetic, an d pathogenic aspects of recessive ataxias is presented. Specific management problems with respect to diagnosis and genetic counseling are discussed.