Extramedullary hematopoiesis

Micrograph showing nucleated red blood cells (bottom left of image), one of the elements necessary to call extramedullary hematopoiesis, in an endometrial polyp. H&E stain.

Extramedullary hematopoiesis refers to hematopoiesis occurring outside of the medulla of the bone (bone marrow).[1]

In some cases, it may be physiologic. For example, during fetal development, hematopoiesis occurs at many different locations, such as the liver and spleen.[2]

However, it is more frequently associated with pathologic processes. For example, it can be caused by myelofibrosis,[3] after fibrotic changes within the bone marrow "crowd out" hematopoietic cells, causing them to migrate to other sites such as the liver and spleen.[4]

Thalassemias, the deficiency of the alpha and beta chains genes, cause extramedullary hematopoiesis. Symptoms include frontal bossing and malar (zygomatic bone/cheek) prominence.

It can sometimes be identified via computed tomography.[5]

See also

References

  1. ↑ Birbrair, Alexander; Frenette, Paul S. (2016-03-01). "Niche heterogeneity in the bone marrow". Annals of the New York Academy of Sciences. 1370: 82–96. ISSN 1749-6632. PMC 4938003 Freely accessible. PMID 27015419. doi:10.1111/nyas.13016.
  2. ↑ Colville J (2000). "Hematopoiesis". Human Hematology (Microbiology 435). North Dakota State University. Archived from the original on December 13, 2008.
  3. ↑ Chunduri S, Gaitonde S, Ciurea SO, Hoffman R, Rondelli D (October 2008). "Pulmonary extramedullary hematopoiesis in patients with myelofibrosis undergoing allogeneic stem cell transplantation. Can induce penile lesions.". Haematologica. 93 (10): 1593–5. PMID 18641018. doi:10.3324/haematol.13203.
  4. ↑ Birbrair, Alexander; Frenette, Paul S. (2016-03-01). "Niche heterogeneity in the bone marrow". Annals of the New York Academy of Sciences. 1370: 82–96. ISSN 1749-6632. PMC 4938003 Freely accessible. PMID 27015419. doi:10.1111/nyas.13016.
  5. ↑ Marchiori E, Escuissato DL, Irion KL, et al. (October 2008). "Extramedullary hematopoiesis: findings on computed tomography scans of the chest in 6 patients". J Bras Pneumol. 34 (10): 812–6. PMID 19009214.


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