Isochromosome X in acute myeloblastic leukemia

Acquired biclonal chromosome X aberrations without autosomal chromosomal anomalies in acute myeloid leukemia

Acquired clonal chromosome X aberrations, whether numerical or structural, as the sole chromosomal anomaly in acute myeloid leukemia (AML) are very uncommon. The scarcity of nonconstitutional chromosome X aberrations detected in AML has prevented any meaningful evaluation of their prognostic significance. In this report, we describe the case of a patient with AML who had the unusual acquired karyotype of 45,X/-X,46,X,i(X)(q10) on presentation and 45,X,-X,add(19)(p13.3) on relapse. We also briefly review the literature on acquired numerical and structural chromosome X aberrations as the sole chromosomal anomaly in AML. This case adds to the sparse body of literature regarding chromosome X aberrations in AML. More case reports are needed to further elucidate the importance of such aberrations.

Isodicentric X chromosomes involving the Xq13 breakpoint in myelodysplasia and acute nonlymphocytic leukemia

Many nonrandom chromosome abnormalities, usually autosomal in nature, have been found to be associated with specific types of acute nonlymphocytic leukemia (ANLL) and myelodysplastic syndromes (MDS). Specific abnormalities involving the sex chromosomes are rare. We have recently identified a structural abnormality of the X chromosome, for example, idic(X)(q13) in three patients: two with MDS progressing to ANLL and one with ANLL de novo. All three patients were elderly females with a very aggressive form of ANLL. Six other patients with a similar abnormality have been discovered in the literature; all having either MDS or ANLL and a short survival. It is suggested that the abnormality identifies a subset of MDS and ANLL occurring in elderly females.

Presence of isochromosomes in hematologic diseases

Several different structural chromosome aberrations have been observed in human neoplasias. In this report we describe the isochromosomes found in nine patients with hematologic malignancies: five with leukemia, one with sideroblastic anemia, and three with malignant lymphomas. The isochromosomes i(7q), i(11q), i(17q), and i(21q) were detected in these patients. We suggest that the presence of isochromosomes permits us to speak of a gene-dosage effect and that this mechanism may play a role in malignant transformation.