What an exciting age for those of us interested in the myeloproliferative
diseases!
Myeloproliferative diseases—a term first used 55 years ago by the famous
hematologist William Dameshek—include chronic myeloid leukemia, polycythemia
vera (PV), essential thrombocythemia (ET), and primary myelofibrosis
(PMF). These are clonal hematopoietic stem cell disorders characterized by the
expansion of one or more cell lines accompanied by varying degrees of marrow
fibrosis.
Slumbering in the diagnostic and therapeutic advances of other areas of
hematology, explosive interest in them began with the exploitation of the molecular
understanding of chronic myeloid leukemia and by the development of the small
molecule, imatinib. This drug not only revolutionized the treatment of chronic
myeloid leukemia, but also stimulated interest in the Philadelphia-chromosome–
negative (Ph−) myeloproliferative diseases because of their clinical and hematologic
similarities. The Ph-negative diseases nevertheless remained in relative
hematologic limbo until the discovery of a molecular abnormality now found in
all patients with polycythemia vera and in about half the patients with essential
thrombocythemia and primary myelofibrosis. This abnormality, found in the
regulatory domain of JAK2, is denoted as JAK2V617F