Chronic myeloid leukemia with permanent disappearance of the Ph1 chromosome and development of new clonal subpopulations

A 6.5-yr follow-up study is reported on a case of chronic myeloid leukemia (CML) diagnosed in 1971 in a man of age of 19 yr. At that time the Ph 1 chromosome was found in all of his bone marrow cells. After 4 yr of intermittent treatment his blood and bone marrow still showed a florid CML picture, but the karyotypes of bone marrow, blood, and spleen cells were normal. Blastic transformation occurred after 5.5 yr and was accompanied by a hyperdiploid karyotype (49,XY,+9,+ 10, + 12) without reappearance of the Ph 1 chromosome. After successful chemotherapy the karyotype again became normal. In 1977 cells with a new clonal aberration (14p+) gradually became the dominating bone marrow cell population, while the peripheral blood was compatible with CML. The 14p+ clone subsequently decreased at the expense of the 49,XY,+9,+ 10,+ 12 clone, which had reappeared in the majority of the dividing blood cells. Also, a new clonal subpopulation 45,XY,t(5p; 17q) was found in 7% of the metaphases. This coincided with the occurrence of a second blast transformation, which was treated with chemotherapy. The karyotypes of all dividing cells during the recovery from the induced severe bone marrow hypoplasia still showed the t(5p; 17q) abnormality and chromosome numbers varying from 45 to 51. In some cells additional trisomies were seen as an indication of a clonal evolution. One month before the patient’s death a fourth abnormal cell line was seen in 10% of the dividing blood cells.