To know KSS, all three things must be there before 20 years old: 1) Eyes muscles slowly getting weak, 2) Back of the eye looks like "salt-and-pepper", and 3) One of these: Heartbeat messes, walking shaky, or brain fluid has too much stuff in it. Genes from body parts (like muscles) can show it for sure by seeing a missing piece of DNA (usually the 4977 bp piece)