Infantile Tay-Sachs, which is fatal, involves a complete lack of a certain enzyme. Late-onset Tay-Sachs involves a deficiency of the same enzyme. It's extremely rare, but probably not as rare as we think, since it gets misdiagnosed as ALS and MS, I think.

My ancestry is 100% Ashkenazi Jewish on both sides. Since my troubles started with a weird gait and balance problems, and since I don't have eye involvement and I'm sero-negative, I may ask my neurologist what he thinks. There's a blood test. But I'm pretty sure that the variability of my symptoms, and the fatiguability, rules it out for me. I also don't have any of the psychiatric symptoms that are often associated with it.

Abby