Abstract
Some patients with aplastic anemia (AA) and approximately 40% of patients with refractory anemia (RA) of myelodysplastic syndrome exhibit karyotypic abnormalities in bone marrow dividing cells. Although some of the patients undergo evolution to acute myeloid leukemia (AML), others follow a clinical course similar to AA patients without chromosomal abnormalities. Except for several abnormalities such as −7 and 5q-, the clinical significance of such chromosomal abnormalities in bone marrow failure patients remains unclear. We recently developed a reliable HUMARA assay capable of detecting a clonal population in granulocytes which constitutes 30% or more of total granulocytes (Blood. 2003;102:1211–1216). Studying correlation between chromosomal abnormalities and the presence of clonality may help in understanding the pathogenetic role of chromosomal abnormalities in AA and RA. We thus analyzed 50 acquired AA and 28 RA female patients who were heterozygous for the HUMARA gene. Chromosomal abnormalities such as add(5)(q13), 9q–9q+ and del(7)(q14q22) were found in 8% of AA and 21% of RA patients. Clonality was detected in 38% of AA patients and 39% of RA patients. Incidence of chromosomal abnormalities in patients with clonality (27%) was higher than that in patients without clonality (4%, p<0.01). In two AA patients who respectively exhibited add(5)(q13) in 10% and +8 in 38% dividing cells, clonality was not detected and these abnormal clones became undetectable at the time of subsequent bone marrow examination. Clonality was detected in the other 2 AA patients respectively exhibiting 9q–9q+ in 40% and del(7)(q14q22) in 25% dividing cells, and in all 5 RA patients respectively exhibiting +8 in 10%, del(5)(q13q31), dup(1)(q32q12) in 90%, del(5)(q13), add(11)(q23), inv(9) in 65% and X,-X in 100% of dividing cells. None of the 50 AA patients including 2 patients with clonality and chromosomal abnormalities underwent evolution to AML during 2-year follow up while one of 28 RA patients who exhibited del(5)(q13q31) progressed to AML. The proportion of clonal granulocytes in total granulocytes estimated by the HUMARA assay remained unchanged in most patients with clonality except for the transformed one. These data indicate that the chromosomal abnormality in bone marrow dividing cells is not necessarily associated with presence of clonal granulocyte population in peripheral blood and that detection of clonality in granulcytes in bone marrow failure patients with chromosomal abnormalities of indefinite significance is useful in predicting prognosis of these patients.
Immunotherapy- (Blinatumomab-) Related Lineage Switch of KMT2A/AFF1 Rearranged B-Lymphoblastic Leukemia into Acute Myeloid Leukemia/Myeloid Sarcoma and Subsequently into B/Myeloid Mixed Phenotype Acute Leukemia
