Trisomy 1q in polycythemia vera and its relation to disease transition.

Clinical and cytogenetic details of 12 patients with polycythemia vera and complete or partial trisomy of the long arm of chromosome 1 are reported. All patients had trisomy for at least the segments 1q22 to 1qter. The 1q or material from 1q was translocated to another chromosome in eight patients. This was chromosome 9 in four patients, and those cases all had trisomy also for 9p. The trisomy 1q was found at the time of diagnosis in three patients, later during the polycythemic phase in five, and in four patients when they were first examined during a late stage of the disease. Acute leukemia or a myelodysplastic syndrome developed in eight of the 12 patients. Signs of advanced disease, eg, myeloid metaplasia or myelofibrosis, preceded the leukemia in four cases and was noted in one more patient. Trisomy 1q was the most frequent structural chromosome abnormality in patients with polycythemia vera. It is thus one of several nonrandom abnormalities that can appear at any stage of the disease. It seems to occur with higher frequency in patients with myelofibrosis and/or leukemia, but it is not a specific characteristic of these complications.