Esp to Lonelycat: About your sister: She may have no symptoms her whole life long or she may have serious ones. My sister , 75, is essentially paralyzed from waist down, has used power chair for at least 15 years. I, 5 years older, didn't show symptoms until 40, started using a cane in my 60s, then a walker, now must use a wheelchair--at least partly because I've also developed scoliosis. The usual reference to women as "carriers" is misleading, because some of us do much more than "carry" the gene/condition. I hope your sister will remain symptom free.