Acute leukemia presenting with extramedullary diseases and completely normal hemogram: an extremely unusual manifestation unique to pre-B ALL.

Acute lymphoblastic leukemia (ALL) is a clonal hematological disease characterized by inadequate normal hematopoiesis secondary to excessive proliferation of leukemic blasts and their impaired differentiation. As a result, patients usually manifest symptoms related to bone marrow failure. It's very uncommon for ALL patients to present with normal hemogram. Herein, we describe two patients who presented with excruciating bone pain at orthopedic clinics. Osteopathy involving multiple bones was noted initially, but acute leukemia was never considered as one of the differential diagnoses because of the completely normal hemogram in both cases. Consequently, the diagnosis of leukemia was slightly delayed. Upon literature review, we found that ALL patients with solely extramedullary diseases and nearly normal hemogram had exclusively pre-B disease. We also propose a putative hypothesis for this interesting finding.