<prompt> All are true about the Etiology of primary myelofibrosis , EXCEPT:JAK2 mutation is seen in 50 casesOverproduction of transforming growth factorOverproduction of osteoprotegerinMutations in the thrombopoietin receptor Mpl occur in 50  <response>: Primary myelofibrosis ,Etiological features. The etiology is unknown. JAK2 V617F is present in approximately 50 of patients Mutations in the thrombopoietin receptor Mpl occur in about 5. Fibrosis is associated with overproduction of transforming growth factor and tissue inhibitors of metalloproteinases Osteosclerosis is associated with overproduction of osteoprotegerin. Ref: Harrison, E-18,P-906. 