Extramedullary hematopoiesis

What it means

The process of hematopoiesis occurring outside of the bone marrow (in the liver, thymus, and spleen) in the postnatal organisms.

During fetal life, the formation of cellular blood components occurs mainly in the liver, shifting to the bone marrow postnatally. Some pathological conditions associated with a severe reduction of marrow hematopoiesis are associated with extramedullary hematopoiesis. The most common causes of Extramedullary hematopoieses (EMH) are myelofibrosis, diffuse osseous metastatic disease replacing the bone marrow, leukemia, sickle-cell anemia, and thalassemia. EMH is usually microscopic and asymptomatic, but it can sometimes manifest as organomegaly and tumor-like masses. Rarely, it can cause cord compression, pleural effusion, massive hemothorax, and respiratory failure.

Rare diseases that can present with this10

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Extramedullary erythropoiesis