Sigbjørn Berentsen, MD, PhD, graduated from the University of Bergen, Norway, in 1973 and had his PhD degree at the same university in 2004. He is currently a consultant hematologist and senior researcher at Haugesund Hospital, Norway, and an emeritus associate professor at the University of Bergen. He had his hematology experience from Haukeland University Hospital in Bergen, Oslo University Hospital, St Olav University Hospital in Trondheim, Stavanger University Hospital, and Haugesund Hospital. Special fields of research interest are autoimmune hemolytic anemia with emphasis on cold agglutinin disease, but also lymphoma and Waldenström’s macroglobulinemia. He is a member of the editorial board of Tidsskr Nor Laegeforen (the Journal of the Norwegian Medical Association), a former editorial board member of Haematologica, and a coauthor of UpToDate. He has published numerous works on cold agglutinin disease together with Norwegian and international co-authors.