MS: is it one disease?

Understanding the molecular pathology of multiple sclerosis (MS) is crucial to interpretation of magnetic resonance imaging appearances in the disease and to developing new therapies. The pathology of MS has always been recognized to be heterogeneous, with the basis of this heterogeneity being hitherto largely attributed to differences in the age of lesions. However, one influential group of researchers put forward the suggestion in 2000 that there are four pathological subtypes of MS that are distinct between cases but consistent within cases. Two more recent attempts to replicate this finding have been unsuccessful, as reviewed by Barnett et al. (this issue, pages 57 to 65). This inability to confirm pathological disease subtypes within the MS disease spectrum is in contrast to recent work on neuromyelitis optica--until recently regarded as part of the MS spectrum--in which evidence from a variety of sources has led to the rapid, widespread acceptance that this condition is indeed distinct from MS. It is important to resolve the outstanding controversies in MS immunopathology and one way to do this might be to conduct a consensus study, a method that has proved valuable in bringing better consistency to the reporting of Alzheimers disease pathology.