PSSM Marshmallow and rocks So there is loads of information out there about PSSM the different variants, how to proceed to test your horse, what does getting the diagnosis mean but I thought I would give you my perspective of working out in the field with horses who have it and how wide the range is when it comes to work, behaviour etc. We are often told this is a new thing and we didn't see this years ago but if anyone has been around horses a while you will at some point heard the vet when exh