Recessive mutations cause a severe form of ataxia, Spinocerebellar Ataxia Autosomal Recessive 1 (SCAR1– OMIM: 606002), which is also known as Ataxia with Oculomotor Apraxia 2 (AOA2); while dominant mutations cause a motor neuron disease known as amyotrophic lateral sclerosis type 4 (ALS4; OMIM: 608465) [1], [2]. The gene discussed is SETX; the disease is spinocerebellar ataxia, autosomal recessive, with axonal neuropathy 2.