Hi Rarity,
Has your husband been tested for PNH?
An elevated LDH is one of the signs (although it can show up for other reasons as well).
AA, MDS, and PNH can overlap. So if your husband's marrow is showing hypocellularity now, it could be another sign of cell destruction.
I found this article that mentions PNH, trisomy 8, and trisomy 21 showing up in PNH/MDS/AA transformation. Unfortunately, it is more observational in nature:
http://www.bloodjournal.org/content/...o-checked=true
Does his hematologist have expertise in PNH?