Cytogenetic evidence for involvement of erythroid progenitors in a child with therapy linked myelodysplasia.

A 6-year-old male with prior metastatic retinoblastoma developed a therapy linked myelodysplastic syndrome. Whole bone marrow cytogenetics showed monosomy 7 and a marker chromosome. To determine the progenitor level of origin of the malignant clone, we studied the karyotypes of marrow erythroid and granulocyte/macrophage colonies grown in methyl cellulose. All erythroid and granulocyte/macrophage colonies had an abnormal karyotype with 45 chromosomes (monosomy 7) and several colonies contained the marker chromosome. These findings give direct evidence that this patient's myelodysplastic syndrome involved an early stem cell which was capable of both erythroid and granulocyte differentiation.