Chromosome Studies in Preleukemia

Abstract Three patients with different obscure hematologic disorders are presented. All 3 patients had abnormalities of chromosome number confined to marrow cells. Case 1 is a 23-year-old man with aplastic anemia; most of his bone marrow cells contained 45 chromosomes, with one missing from group C. Case 2 is a 62-year-old man who died of idiopathic sideroachrestic anemia; most of his bone marrow cells contained 47 chromosomes with an extra C group chromosome which appeared to be an autosome. Case 3 is a 59-year-old woman with idiopathic thrombocythemia; while the majority of her bone marrow cells contained 46 chromosomes, a stable minority cell line had 48 chromosomes. Although many of the reported patients with myelodysplastic-myeloproliferative disorders have normal chromosomes, 5 cases with some chromosomal aberration, previously reported by others, are summarized. None of these patients had clinical evidence of leukemia. In 4 of the patients, the chromosomal anomaly involved a chromosome in group C, which is the group in which aneuploidy occurred in all 3 of our patients. It is postulated that a stable, aneuploid stem line does not of itself produce neoplasia, but rather that this alteration of the genome may provide a more favorable milieu for the action of some transforming agent. Because of the frequent occurrence of C group abnormalities in these cases of marrow disorders, it is further postulated that genes on one or more C chromosomes might be responsible for homeostatic control of hemopoiesis, and that a change in genetic balance involving a C group chromosome(s) coupled with a transforming agent might result in leukemia in a greater proportion of individuals than aneuploidy of some other chromosomal group.