 Normally, no one knows why anyone has it. 90% of cases are unknown, but 10% are actually familial with a genetic marker. So we learned she died of familial ALS, and there is, at this point, a 50-50 chance that my husband will have it. Did her parents have it? There's no way to know. Her father had it, and she has a sister that also died from it. Oh, Heather, I'm so sorry.