SMS and syndromic X-linked intellectual disability Snyder type: Furthermore, mutations, whichresult in reduced activity of spermine synthase, are associated with the raregenetic disease, Snyder-Robinson mental retardation syndrome (OMIM #309583) [33,34].This X-linked disease is characterized by cognitive and developmental abnormalities.The links between loss of enzyme activity and this pathology have not been fullyelucidated.