Cutaneous extramedullary hematopoiesis is a rare cutaneous manifestation of myelofibrosis, where hematopoiesis occurs in the skin rather than the bone marrow, causing polymorphic skin lesions. The condition most often presents as bilateral lower extremity ulcers, but it may also cause papules, nodules, and plaques on any body part. These lesions typically begin as pink erythematous lesions, which become violaceous, hemorrhagic, and ulcerated over time. In addition, the lesions also tend to increase in number and size if the underlying hematological condition remains untreated.

(Of note, cutaneous extramedullary hematopoiesis is a normal occurrence during early embryogenesis, and it occurs until about the fifth month of gestation. Cutaneous extramedullary hematopoiesis in pre-term or full-term neonates is thought to be an accentuation of a normal physiologic process. These lesions resolve spontaneously 3-4 weeks after birth without intervention. Multiple reports suggest also that cutaneous extramedullary hematopoiesis in neonates may be precipitated by congenital infections, erythroblastosis fetalis, and twin transfusion syndrome.)