Primary myelofibrosis with or without mutant MPL: comparison of survival and clinical features involving 603 patients

MPL and JAK2 V617F mutation analysis was performed in 603 patients with primary myelofibrosis (PMF) seen at the Mayo Clinic, USA ( n =329) or University of Florence, Italy ( n =274). Mutant MPL was detected in 49 (8.1%) patients and JAK2 V617F in 350 (58%); 4 patients showed both mutations. MPL W515L/K was the commonest mutation; 2 patients showed novel mutations ( L513ins and Q516-P518insAAAA ). The US and Italy patient cohorts were separately analyzed for comparison of survival and clinical features between MPL -mutated, JAK2 -mutated and JAK2/MPL -unmutated cases. JAK2/MPL -unmutated patients were significantly younger than their JAK2 -mutated counterparts, in both patient cohorts ( P