Clonal analysis of chronic myeloproliferative disorders using X-linked DNA polymorphisms.

Restriction fragment length polymorphisms of the X-chromosome genes phosphoglycerate kinase and hypoxanthine phosphoribosyl transferase were used to study clonality in peripheral blood leukocytes from 48 women with chronic myeloproliferative disorders (c-MPD). A total of 50% of patients were heterozygous for one or both of the polymorphic loci. These included 17 cases with polycythemia vera, four patients with essential thrombocythemia (ET), and three cases with idiopathic myelofibrosis (IMF). A clear-cut monoclonal X-inactivation pattern was observed in 17 of 24 cases including all IMF patients. Only one patient with PV exhibited a nonclonal composition of her leukocytes, while six cases demonstrated a predominantly clonal pattern in peripheral blood cells. Among the latter category reckoned three of four ET patients. Cell separation analyses were performed in one ET and three PV patients. In all four cases a monoclonal pattern of the granulocyte fraction could be established, while T lymphocytes of these patients were of nonclonal origin. These data suggest that the vast majority of c-MPDs arise from multipotent hematopoietic stem cells. Moreover, this type of clonal analysis might be of help in discriminating between primary MPD and reactive processes.