Translocation t (8;21) associated with marked granulocytic hyperplasia

A 16-year-old boy with leukemia had a marked leucocytosis (165 x 10(9)/L) at presentation. The large number of neutrophils, myelocytes, and metamyelocytes and negative leucocyte alkaline phosphatase reaction raised the possibility of chronic myeloid leukemia. Cytogenetic analysis showed a deletion of chromosome 7, a t (8;21), a missing Y chromosome, and, in some cells, duplication of the der(21). The Philadelphia chromosome was not detected, nor was the breakpoint cluster region of chromosome 22 found to be rearranged. Myeloid leukemia with t (8;21) can therefore be associated with a greater degree of granulocytic hyperplasia than has so far been apparent, and cytogenetic analysis in this case has been crucial in distinguishing leukemia types.