Based on these abnormalities, they are classified as Essential thrombocythemia (increased platelets) Primary myelofibrosis (marrow fibrosis or scarring) Polycythemia vera (any combination of increased WBCs, RBCs, and platelets but rarely erythrocytosis alone) Chronic myeloid leukemia (associated with the Philadelphia chromosome and expression of BCR / ABL fusion gene) Essential thrombocythemia, primary myelofibrosis, and polycythemia vera can spontaneously transform to acute leukemia.