The Chromosomes in Polycythaemia Vera

There have been few previous cytogenetic studies of patients with polycythaemia vera (P.V.). Nowell and Hungerford (1962) and Nowell (1965) investigated the chromosomes of the bone marrow and peripheral blood in five patients with polycythaemia who had been treated with radio‐phosphorus (32P). They found abnormal cell lines in four patients, one of whom had developed leukaemia. Kemp, Stafford and Tanner (1961) examining the bone marrow by the short‐term culture method, found that seven out of nine cases of polycythaemia were normal, one patient had a cell line of 48 chromosomes, and one patient (who subsequently developed frank chronic granulocytic leukaemia) showed Ph1‐positive cells. Both these patients had been treated with 32P. An abnormal clone having a deletion of one of the C group chromosomes was present in the bone marrow of a patient with P.V. (Solari, Sverdlick and Viola, 1962): this patient had received X‐rays and 32P. Levan, Nichols, Hall, Löw, Nilsson and Nordén (1964), using the blood leucocyte culture method, found hyperdiploid cell lines in a male patient with P.V. who had received 32P. He had a few features of chronic granulocytic leukaemia. In all these previous studies, it is not known to what extent the chromosomal abnormalities are due to the disease or are secondary to treatment. It is clearly established that 32P produces typical radiation damage of the chromosomes of blood leucocytes (MacDiarmid, 1965). A few cases of P.V. have been investigated in the terminal stages of the disease, after the development of a leukaemic state (Ford, Jacobs and Lajtha, 1958: one case; Baikie, Jacobs, McBride and Tough, 1961: two cases). In each case, short‐term bone‐marrow culture showed hypodiploid counts.