Karyotypic patterns and their clinical significance in polycythemia vera.

We studied a series of 34 polycythemia vera (PV) patients to determine the incidence of chromosome abnormalities and their relationship to leukemic transformation. Metaphase chromosomes from bone marrow or unstimulated peripheral blood were examined with conventional stain and, in 20 patients, also with banding techniques. The overall incidence of clonal abnormalities in first samples was 44% (15 of 34 patients), with a higher incidence in patients who had received prior therapy. The most frequent abnormalities were long-arm deletion of No. 5 (5q-; four patients), gain of all or most of a No. 8 (five patients), gain of all or most of a No. 9 (four patients), and long-arm deletion of No. 20 (three patients); these sometimes occurred in combination. Some of the PV patients who had cytogenetic abnormalities early in the disease have had long survivals without developing leukemia. For example, one patient has been 48,XX,+8,+9 in sequential samples obtained over the last 15 years. Five patients developed acute myeloblastic leukemia (AML); each had a complex chromosomal pattern. Two of these five patients were cytogenetically normal during the polycythemic phase; the change in karyotype occurred with the leukemic transformation. Three AML patients were studied only in the leukemic phase. Three AML patients had a 5q-, and a fourth showed loss of a B-group chromosome. Evolutionary changes in the karyotype during the disease course and the occurrence of a 5q- appear to be associated with a terminal phase of PV.