Leukocyte Alkaline Phosphatase and the Philadelphia Chromosome

Abstract

CHRONIC myelogenous leukemia (CML) is the only malignancy in which a specific and consistent chromosome abnormality has been consistently documented.1This cytogenetic abnormality, designated the Philadelphia (Ph') chromosome, appears to be limited to CML2-5or closely related variants.6Therefore, its demonstration may be regarded as at least presumptive evidence for this disease. Another characteristic of CML is the depressed level of the leukocyte alkaline phosphatase activity (LAP).7An elevated LAP in a myeloproliferative disorder has been generally assumed to exclude a diagnosis of CML.8Recently, however, both Rosen and Teplitz9and Heath and Moloney10have reported elevated LAP levels in patients with Ph' positive CML coexisting with a second disorder. These two reports suggest that elevated enzyme values may occur in CML if the leukemic process is accompanied by another disease. The present paper describes the third case of an elevated LAP in a Ph' positive CML in the presence