Duplication of part of the long arm of chromosome 1 in marrow cells of a treated case of myelomatosis.

In a case of classical myelomatosis treated with melphalan, a clone of cells with a chromosomal abnormality was found in the bone marrow during remission. There was good reason to think that the hemopoietic cells, rather than plasmacytoma cells, were implicated. Although the clone persisted, no evidence of leukemia developed over a period of observation of 2 yr. The anomaly was interpreted as a duplication of part of the long arm of chromosome 1, which appeared to involve the segment q21 to q31.