Subdural hemorrhage secondary to extramedullary hematopoiesis in postpolycythemic myeloid metaplasia.

A 64-year-old woman with a 20-year history of polycythemia vera and a 2-month history of postpolycythemic myeloid metaplasia ( PPMM ) became comatose because of bilateral subdural hematomas. Biopsy of the dura mater at operation demonstrated extramedullary hematopoiesis ( EMH ). The subdural hemorrhage was secondary to dural invasion by hematopoietic tissue and vascular dilation with a predisposing element of thrombocytopenia. This is the second case of central nervous system (CNS) EMH in a case of polycythemia vera. Only 8 cases of symptomatic CNS EMH and 16 cases overall have been reported, and these were primarily due to agnogenic myeloid metaplasia. Symptoms were secondary to the mass effect of dural tumor-like hematopoietic tissue or to an elevated cerebrospinal fluid protein content. The survival after a diagnosis of PPMM with CNS EMH has been less than 6 months in all cases. CNS EMH is an unusual and a potentially critical complication of polycythemia vera that should be considered in the evaluation of the patient with polycythemia vera and myeloid metaplasia.