The objective of this study is to determine whether pomalidomide is safe and effective in reversing red blood cell (RBC)-transfusion-dependence in persons with myeloproliferative neoplasm (MPN)-associated myelofibrosis. (Global Study) and to describe the frequency of anemia response to pomalidomide in Chinese participants with MPN-associated myelofibrosis and severe anemia not receiving REC-transfusions (China Extension Study only)