when I saw "Stiff-Person Syndrome" I thought this must be about AS, but it's another immune disorder, I've never heard of it before, pity we didn't think of that name first!!
http://www.docguide.com/news/content.nsf/news/852576140048867A8525765000731DB7
Study Shows Negative Results of Rituximab in Patients With Stiff-Person Syndrome: Presented at ANA

By Crina Frincu-Mallos, PhD

BALTIMORE, Md -- October 15, 2009 -- In contrast to promising results in other autoimmune disorders, rituximab is ineffective in treating stiff-person syndrome (SPS), an immune-mediated disorder characterised by rigidity of limb muscles and spasms...........