Karyotype Instability in Myelodysplastic Syndromes-A Specific Step in Pathogenesis Preceding Clonal Chromosome Anomalies

Abstract
In a prospective study, 20 (11.6%) out of 172 patients with myelodysplastic syndromes (MDS) and two patients with aplastic anemia showed an increased spontaneous karyotype instability. No clonal chromosomal aberrations were detectable at the time of first examination. In three patients clonal anomalies developed during the course of the disease. In 17 out of 22 cases (77.2%) chromosomes 1, 5 or 7 were involved in nonclonal anomalies. The same chromosomes were frequently affected in patients with clonal abnormalities too. Our data suggest that spontaneous karyotype instability may be specific to a high proportion of cases with MDS and may constitute the source of clonal chromosome anomalies in these disorders.