Extramedullary hematopoiesis

hematopoiesis (blood cell formation) outside of the bone marrow (the medulla)

Description
Extramedullary hematopoiesis is a physiological process during, e.g., human intrauterine development, when the sites of blood-cell production shift from yolk sac to liver, spleen and finally the bone marrow, the prevailing cite of hematopoiesis in the adult. Illness, such as myelofibrosis or anemias may cause hematopoiesis in the adult outside the bone marrow. Extramedullary hematopoiesis is a hallmark of untreated thalassemia and leads to systemic massive expansion of erythropoietic cells with numerous, severe medical consequences, such as compression of the spinal cord and partial paraplegia.