A Marrow Chromosomal Abnormality Preceding Clinical Leukemia in Down’s Syndrome

During a routine diagnostic cytogenetic study of the marrow of a child with Down’s syndrome, a minor line of cells with a complement of 50 chromosomes was discovered. The predominant cell in marrow and blood had 47 chromosomes with the standard trisomy in Group 21-22. Although anemia and thrombocytopenia were present, other diagnostic criteria of leukemia did not appear until several weeks later. It is proposed that careful cytogenetic studies combined with serial clinical evaluation may disclose important relationships between chromosomal mutation, aneuploid stemlines, and the production and evolution of neoplasms.