Acute Megakaryoblastic Leukemia With Diffuse Periosteal Reaction of Bilateral Lower Extremities.

We report the case of a 3-year-old girl diagnosed with acute megakaryoblastic leukemia, who presented after >1 year of bilateral leg pain. At times the pain was severe enough to prevent ambulation, prompting visits to her primary care provider. However, it was not until acute respiratory failure occurred with subsequent hospitalization in the pediatric intensive care unit that severe anemia and thrombocytopenia were discovered and the diagnosis of acute myeloid leukemia was made. Bilateral lower extremity swelling was noted on admission and radiographs showed diffusely abnormal appearance of the long bones of her lower extremities with periosteal reaction and echogenic debris in the subperiosteal space, thought to represent leukemic cells. This case highlights the importance of recognizing atypical signs and symptoms of myelodysplastic syndrome progressing to acute leukemia in the context of abnormal bone pain and radiographic changes.