1. Comprehensive Cancer Center, Rotterdam, The Netherlands
2. Centro Trapianti di Midollo Osseo, Divisione di Ematologia II, Ospedale San Martine, Genova, Italy
3. Rheumatologische Universitätklinik Basel, Felix Platter‐Spital, Basel, Switzerland
4. Department of Neurology, University of Texas, Houston Health Science Center, Houston, Texas, USA
5. The New York Hospital‐Cornell Medical Center, Department of Neurology and Neuroscience, New York, New York, USA
6. International Bone Marrow Transplant Registry and Autologous Blood Marrow Transplant Registry, North America, Statistical Center, Medical College of Wisconsin, Milwaukee, Wisconsin, USA