Intracranial Extramedullary Hematopoiesis in a Recently Recovered Monkeypox Patient: A Case Report

Abstract Extramedullary hematopoiesis (EMH) is a compensatory response wherein blood cell production occurs outside the bone marrow, typically as a result of hematologic disorders that impair bone marrow function. Conditions such as myelofibrosis, thalassemia, and sickle cell disease often lead to EMH in organs like the liver and spleen, which serve as alternative sites for hematopoiesis. This case report highlights the importance of considering EMH in the differential diagnosis of intracranial lesions, exemplified by a 67-year-old woman who presented with headaches and generalized malaise. Her medical history included hypertension and mild anemia. Magnetic resonance imaging (MRI) revealed a cystic mass in the right inferomedial parietal lobe, which showed medial mural enhancement, edema, and mass effect, with an additional enhancing focus in the left parietal lobe. Initially suspected to be a hemangioblastoma, the resected mass was found to be a benign vascular lesion with endothelial hyperplasia, but without the characteristics of cavernous hemangioma or vascular malformation. The histopathological examination revealed foci of erythroid and myeloid precursors, and megakaryocytes, with immunohistochemical staining confirming the diagnosis of EMH. Subsequent investigations revealed no underlying hematological disorders, leading to a diagnosis of idiopathic intracranial EMH. The patient underwent intensity-modulated radiation therapy (IMRT) for the remaining lesion and showed significant improvement in symptoms at three months follow-up. This case underscores the diagnostic challenges associated with intracranial lesions and highlights the necessity of considering EMH, particularly when faced with atypical imaging and histopathological features. Future research is needed to optimize therapeutic strategies and assess long-term outcomes for intracranial EMH.