Summary. An analysis was made of the chromosomes of 1301 marrow cells from 59 haematologically normal men and women. No case of total aneuploidy was found. The overall incidence of aneuploidy in the population of 1301 marrow cells was 10.3%; hypodiploid 10%, hyperdiploid 0.3%. In the group of 15 individuals where 50 cells could be analysed the proportion of aneuploid cells differed very significantly from person to person. In contrast to the situation in myeloproliferative disorders, hyperdiploidy in normal bone marrow cells was rare. The significance of differences between normal bone marrow cells and normal blood lymphocytes and between normal bone marrow cells and those in chronic myelo‐proliferative disorders is discussed. A significant loss of G‐group chromosomes in the aneuploid cells of the two oldest males (73 yr) was demonstrated. There was a low incidence of chromosomal and chromatid aberrations.

Ph1 positive leukaemia was diagnosed in eight of 123 (6.5%) consecutive new cases of childhood leukaemia. Four patients presented as typical chronic granulocytic leukaemia (CGL) and four as acute leukaemia, two of the four children with CGL have since developed blast crisis. Morphological and immunological characterization of the blasts in these six acute cases was suggestive of a lymphoid crisis in three, a mixed crisis in two, and a myeloid crisis in one. Remission was achieved in five of the six patients but lasted more than a year in only two; in one of these two patients the blasts at the time of crisis lacked the Ph1 chromosome and in the other, who presented in myeloid crisis, remission ended in a lymphoid crisis. Cytogenetic studies showed unusual translocations in two of the eight children. Serial examination showed that three children the proportion of Ph1 positive cells in the marrow was reduced to less than 6% at the time of remission from acute leukaemia. We conclude that Ph1 positive leukaemia in childhood presents frequently as acute leukaemia and may even mimic 'good risk' acute lymphoblastic leukaemia. The response to treatment cannot be predicted by morphological or immunological characterization of blast cells. Storage of bone marrow for possible autologous transplantation should be considered in children who achieve remission.

A case report of serial chromosome studies on a child presumed to have acute lymphoblastic leukemia (ALL) is presented. Hematologic remission was achieved after 3 weeks and maintained until death 63 weeks later. The classic Philadelphia chromosome translocation was found, both at diagnosis and throughout the course of the disease, in a proportion of cells from PHA-stimulated blood cultures. The finding is related to other reports of Philadelphia-positive clones in ALL, as well as those in chronic myeloid leukemia and its acute transformation, and other myeloproliferative disorders. The origin of the Philadelphia chromosome in this case is considered in the light of current stem cell theory, and its relevance to lymphocytic neoplasia is discussed. We believe that the finding of a Ph1-positive clone in a cell line morphologically indistinguishable from normal lymphocytes in a case of acute leukemia is unique.