Although the mechanism that favors emperipolesis in GPS is still far to be elucidated, some evidences suggest a mechanism similar to that described in primary myelofibrosis in humans, involving the mislocalization of P-selectin on megakaryocyte membrane favoring the interaction with leukocytes through the PSGL-1 countereceptor and their trapping within the megakaryocyte cytoplasm33, 34. This evidence concerns the gene SELP and primary myelofibrosis.