Philadelphia chromosome-positive chronic myelogenous leukemia following apparent acute lymphoblastic leukemia

The observation that Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL) may progress to chronic myelogenous leukemia (CML) has been well-documented among adult patients but reported only rarely in children. In this report, we describe a pediatric patient with atypical ALL, who subsequently went on to develop classical adult-type CML. This patient is unique and important because of the unusual clinical findings that she exhibited during the "ALL" phase, namely, extreme thrombocytosis, marrow fibrosis, and persistent splenomegaly, which heralded the onset of frank CML. It is suggested that the patient with presumed, but atypical, ALL be carefully evaluated for CML presenting in lymphoblastoid crisis, and that all patients with the morphologic diagnosis of ALL undergo complete cytogenetic and immunologic marker studies to confirm the diagnosis.