Résumé
Ataxia with oculomotor apraxia (AOA) is a newly recognized group of recessive ataxias that associate ataxia due to cerebellar atrophy with peripheral sensorimotor neuropathy. Unlike what the name suggests, oculomotor apraxia is not an absolute feature of AOA but is a useful diagnostic aid when present. This chapter discusses recessive ataxia plus oculomotor apraxia syndromes. Molecular genetic studies have delineated a novel group of recessive ataxias defined by the association of cerebellar atrophy and peripheral sensorimotor neuropathy. This group includes ataxia with oculomotor apraxia form 1, defined by late hypoalbuminemia and hypercholesterolemia; ataxia with oculomotor apraxia form 2, defined by moderately elevated serum α-fetoprotein (AFP); ataxia-telangiectasia-like disease without elevated serum AFP; and spinocerebellar ataxia with neuropathy (SCAN1), also associated with late hypoalbuminemia. For all four inherited diseases, the gene encodes for a nuclear protein (aprataxin, senataxin, MRE11, and tyrosyl-DNA phosphodiesterase, respectively), which is or may be involved in DNA repair, although the disease causing mutations do not result in cancer predisposition.