In leukemoid reactions, there is a distinct reactive and therefore nonmalignant leukocytosis with immature stages of granulopoiesis.
Leukemoid reactions occur mostly in severe acute and chronic infections. The leukemoid reaction occurs more often in children. The leukemoid reaction must be distinguished from chronic myelocytic leukemia.
Metamyelocytes and myelocytes are present in the peripheral blood. This is usually associated with leukocytosis (> 20 x 109/L). Normal or low leukocyte values in the course of a leukemoid reaction suggest failure of myelopoiesis.