Cutaneous extramedullary haematopoiesis: Implications in human disease and treatment.

The skin and bone marrow are two of the most dynamic organ systems of the human body. While the skin is only transiently involved in haematopoiesis in utero, cutaneous extramedullary haematopoiesis (CEMH) has been appreciated in various neonatal and adult diseases. The mechanism by which CEMH occurs remains poorly understood, but may be associated with the plasticity of blood and skin tissues. Extensive studies have documented expansion and differentiation of haematopoietic lineages from cutaneous tissues and vice versa. This review will discuss CEMH, potential mechanisms and laboratory findings that shed light on the interaction between both tissues. Further, we will discuss the implications of understanding the role of the skin in haematopoiesis, including the potential therapeutic function of manipulating either organ system in the treatment of pathologic processes in the other.