The Ph1 chromosome in childhood leukaemia.

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.