Submetacentric Chromosome in Chronic Myelocytic Leukemia

Introduction  A chromosomal aberration has been described in chronic myelocytic leukemia.^1-7 This abnormal chromosome appears to belong to the small acrocentric chromosome group with deletion of part of the long arms of one of these chromosomes. It has been named "Philadelphia" or "Ph¹." In addition to this chromosome found in chronic myelocytic leukemia, another small, minute chromosome has been reported in a case of this disease.⁴ Recently, Warkany et al ⁸ reported chromosome analysis of a case of mongolism associated with acute myeloblastic leukemia. They found a typical trisomy-21 mongolism in this patient; but, in addition, an extra medium-sized submetacentric chromosome was found in the cells cultured from the peripheral blood leukocytes. This chromosome resembled the chromosomes of the group 6-12 and X of the Denver classification.⁹ Additional chromosomes of similar morphology have been reported in cases of acute myeloblastic leukemia.^10,11A patient with chronic