Cytogenetic patterns in polycythemia vera

The incidence of clonal chromosome abnormalities in bone marrow cells of patients with polycythemia vera (PV) varies with the stage of their disease. Thus, fewer than 15% of patients have abnormalities prior to myelosuppressive therapy, whereas the incidence is 35-40% in initial samples from treated patients. Some PV patients develop leukemia late in their disease course; more than 80% have abnormal karyotypes at this time. Gains of chromosomes are usually seen in abnormal clones from untreated PV patients, and therefore the modal number is generally hyperdiploid. Structural rearrangements are more frequent in clones from treated patients, which are typically pseudodiploid. Analysis of chromosomal banding patterns in PV reveals that certain nonrandom abnormalities occur, including +8, +9, 20q-, and trisomy of 1q. Although the 20q- is a frequent finding in PV, this abnormality has also been reported in patients with various other myeloid disorders.