SMA is caused by a defect in the survival motor neuron one gene. The most efficient one is called SMN 1 – that’s what’s missing in spinal muscular atrophy,” said Dr. Ann Tilton, a child neurologist at LSU Health Science Center in New Orleans. Evrysdi is the first and only oral medication approved by the FDA. Nearly all U.S. states are now screening newborns for SMA.