SETX and proximal spinal muscular atrophy: Mutations in Senataxin gene (SETX) also cause two distinct juvenile-onset hereditary neurological diseases, Ataxia with Oculomotor Apraxia type 2 (AOA2) [7] and Amyotrophic lateral sclerosis type 4 (ALS4) [8], and in addition, defects in Senataxin function have been associated with the neuromuscular disorder Spinal Muscular Atrophy (SMA) [9].