SMN2 and proximal spinal muscular atrophy: The most advanced clinical trials for SMA are focused on increasing SMN protein level by upregulating the production of full length protein from the SMN2 gene (d’Ydewalle and Sumner, 2015), and the first, very costly, drug to specifically treat SMA was approved by the U.S. Food and Drug Administration in December 2016 (Aartsma-Rus, 2017), 125 years after the first description of this disease.