Leukoerythroblastic anemia is any anemic condition resulting from space-occupying lesiosn in the bone marrow; the circulating blood contains immature cells of the granulocytic series and nucleated RBC's, frequently in numbers that are disproportionately large in relation to the degree of anemia.

• It can be the bone marrow's response to any irritation, including marrow infiltration, causing immature RBC's. Marrow infiltrative disorders include myelomas, malignancy, myelofibrosis, Gaucher's disease, etc
• It can also cocur as a response to severe critical illness, e.g. trauma, septicemia, massive hemolysis, or severe megaloblastic anemia
• Leukoerythroblastic changes refers to the presence of nucleated RBC's and primitive WBC's