Acute Lymphoblastic Leukemia With Eosinophilia Lacking Peripheral Blood Leukemic Cell: A Rare Entity

We describe a 57-year-old woman who was diagnosed as precursor B-cell acute lymphoblastic leukemia with marked eosinophilia (ALL-eo). She presented with low grade fever and eosinophilia (absolute count 16.5 × 109/l). Most of eosinophils had hypogranular cytoplasm. Immature cells were absent in her peripheral blood. Since her platelet count was low, bone marrow examination was carried out. 57.2 % of nucleated cells were blastic cells positive for CD10, 19, and 20. Chromosomal analysis revealed a karyotype of 46,XX,t(5;14)(q31;q32). Despite induction chemotherapy, her disease progressed and she died of sepsis a month later. ALL-eo is extremely rare and the diagnosis might be delayed unless leukemic cells are seen in peripheral blood. Therefore, bone marrow should be examined as soon as possible in cases with eosinophilia not only for the differential diagnosis of eosinophilic disorders but also not to overlook ALL-eo.