Cytogenetic evidence for involvement of erythroid and granulocyte/macrophage progenitors in an infant with monosomy 7 syndrome presenting de novo.

Monosomy 7 presenting as a myelodysplastic syndrome following radiation and chemotherapy has been reported to involve a stem cell capable of both erythroid and granulocyte/macrophage differentiation. To determine if monosomy 7 presenting de novo also involves a multipotential stem cell, we examined mitoses from individual colony-forming units (CFU)-GM and burst-forming units (BFU)-E colonies derived from semisolid cultures of marrow from an infant with this disorder. Direct cytogenetic analysis of bone marrow cells disclosed the characteristic 45,XY,-7 karyotype in 32 of 35 abnormal metaphases. Metaphases were obtained from 63 (73%) of 85 CFU-GM and BFU-E colonies (median metaphases per colony = 4, range = 1-21), with well-banded analyzable chromosome spreads available for 15 of the colonies with metaphases. The monosomy 7 karyotype was present in all 14 metaphases from ten BFU-E colonies and in all seven metaphases from five CFU-GM colonies. These results indicate that the monosomy 7 karyotype can originate in haematopoietic stem cells with both erythroid and granulocyte/macrophage differentiative potential.