Footnotes

• Contributors MC, AS, MR, FC and CB are the neurologists in charge of the patients at the University of Padova. LB and MG are the neurologists in charge of the patients at the University of Genova. ENO and MB are the neurologists in charge of the patients at the Humanitas Center in Rozzano, Milan. GAM and GM are the neurologists in charge of the patients at the University of Tor Vergata, Rome. NR and RF are the neurologists in charge of the patients at the San Raffaele Hospital, Milan. RZ is the haematologist in charge of most of the patients. ME is a neurologist, who did the statistical analysis. CB, MC and RZ are the persons who designed the study and wrote the draft of the manuscript.

  All the authors helped in the acquisition, analysis and interpretation of data, as well as in critically revising the manuscript for important intellectual content. All the authors have read and approved the final version of the manuscript.

• Competing interests None declared.

• Ethics approval Local ethics committees.

• Provenance and peer review Not commissioned; externally peer reviewed.