Nucleated red blood cell

NRBCs are normally found in the bone marrow of humans of all ages and in the blood of fetuses and newborn infants.

The presence of circulating NRBCs in adults occurs in situations of hematopoietic stress such as severe infection, massive hemorrhage, marrow infiltration, or extramedullary hematopoiesis.

Possible pathologic causes include anemia, myelofibrosis, thalassemia, miliary tuberculosis, cancers involving bone marrow (myelomas, leukemias, lymphomas), and in chronic hypoxemia.

This kind of anemia leads to macrocytes (abnormally large red cells) and the condition called macrocytosis.

The cause of this cellular gigantism is an impairment in DNA replication that delays nuclear maturation and cell division.