I have PPMS and have always thought it was a different manifestation of the same disease as RRMS. I have never understood why Secondary Progressive MS is different from Primary Progressive MS except that it starts after a period of RRMS. If, as I believe and seems to become more supported by data, MS is not really an autoimmune disease, but something else causes the demyelination of the brain tissue and then an inflamitory response is generated to "clean up" celular debris, and that looks like an immune activity and has been misinterpreted as the cause of the demyelination, it would seem to make sense that the initial demyelination from whatever cause is probably the disease, and the fact that some people remit and are diagnosed as RRMS and some people do not, and are thus diagnosed as PPMS or SPMS, it is probably the same disease.
The inflamation and remisssion may have more do do with the permiability of the BBB to the inflamatory cells in the blood stream, and whatever is causing the demlyelination (e.g. CCSVI!!) can exit without sufficient inflammatory activity to relapse and remit.
This is my logic, and not really supported by alot of data that I can think of. Does anyone know if the permiability of the BBB is different between PPMS and RRMS?