Hi Amy,
I also don't quite fit the profile of either AA or MDS. My first BMB was 20% hypocellular with no dysplasia. My third, done a month later, was normalcellular with 10% dysplasia. So, my doctors don't know what to make of me. I do not have chromosonal abnormalities.
I know that ATG in combination with CsA has been shown to be effective in some people with hypocellular MDS - particularly MDS-RA. Duration of the response is debatable though. I've heard everything from 6 months to 15 years! This is the treatment that I received 4 months ago, and I've seen a hematological response in that I no longer need transfusions but my counts are still low.
Here is a good article on using ATG/CsA for MDS. It gives profiles of the different patients and who responded:
http://www.nature.com/leu/journal/v1.../2403124a.html
There was a recent study completed comparing ATG/CsA with using CsA alone for the treatment of hypocellular MDS. CsA alone can be effective, but the probability of response is less than when used in combination with ATG. Here's an abstract from that study:
http://www.ncbi.nlm.nih.gov/pubmed/18413642
Responses are more likely in younger patients with low ipss scores and hypocellular MDS-RA. (Do you know your mom's subtype?)
Are you in the position to get another opinion before beginning the treatment protocol? It is a tough call. CsA alone is the least toxic approach, but has a lower probability of response than when used in combination with ATG. Also, they will likely want to wait 3-6 month after starting the CsA before trying another approach.
I hope this helps a little. I'm not a doctor - just learning as I go!
I wish you both the best!