Isodicentric X chromosome in myeloproliferative disorders.

Two further cases of acquired isodicentric (X)(q13) chromosome in patients with myeloproliferative disorders are reported. One patient had a primary myelofibrosis and the other a chronic myelogenous leukemia. DNA replication study demonstrated that both abnormal X chromosomes were late replicating in all cells examined. The inactive condition of idic(X)(q13) seems to be indicative of a selective advantage for a cell carrying this alteration.