Acute Lymphoblastic and Acute Myeloid Leukemia

Acute leukemia is a clonal malignancy in which immature blood-forming cells multiply and fail to mature normally. These blasts accumulate in the marrow, crowding out functional red cells, platelets, and neutrophils. The massive proliferation of nonfunctional blasts causes bone marrow failure: anemia, thrombocytopenia, and neutropenia. That mechanism explains a seemingly contradictory presentation: a patient may have a very high white-cell count and still be profoundly infection-prone. The circulating cells may be mostly blasts, not mature neutrophils capable of phagocytosis. A low or normal white-cell count does not make acute leukemia less likely. ALL arises from lymphoid precursors, whereas AML arises from myeloid progenitors. Both can cause fatigue, exertional dyspnea, fever, recurrent infection, bruising, petechiae, mucosal bleeding, bone pain, lymphadenopathy, and splenomegaly. AML is more likely to produce myeloid tissue infiltration, such as gingival enlargement or skin lesions. ALL carries particular concern for CNS involvement, so CNS-directed therapy is built into treatment. The first bedside pattern is therefore marrow failure, not the absolute white-cell count. Ask whether fatigue reflects anemia, whether fever reflects neutropenia, and whether bleeding reflects thrombocytopenia. Then look...