Usefulness of RA and RO Isoforms of Common Leukocyte Antigen (CD45) for Early Distinction Between Normal and Abnormal Promyelocytes

Normal promyelocytes express CD45RO, while acute promyelocytic leukemia (APL) blasts express CD45RA, both isoforms of common leukocyte antigen with mutually exclusive expression. Here we report a patient with accumulation of promyelocytes in the bone marrow and the diagnostic strategy is described along with the ability to quickly discriminate between normal and abnormal cells using the flow cytometric detection of expression of RA/RO isoforms of CD45.