renal extramedullary hematopoiesis. case reportExtramedullary hematopoiesis (EMH) is defined as the formation and development of erythrocytic, granulocytic and megakaryocytic cell lines outside the bone marrow; it is a rare occurrence, which is limited to case reports.objective: To describe a case of renal EMH secondary to chronic hypoxia.case report: The patient is a 16 year old teenager who developed chronic hypoxia, central cyanosis, clubbing and lives more than 2,500 m above sea level.Chronic hypoxia is probably secondary to pulmonary hypertension, neither detected nor previously treated.The Consultation was due to a mass in the left upper quadrant for the last three months.An Echocardiogram showed pulmonary hypertension that could not be assessed by hemodynamic parameters.A computed tomography showed bilateral left renal pelvic masses.The hemogram showed polycythemia, so bone marrow aspiration was performed, which rule out malignant pathology.A biopsy of the renal mass reported EMH with three hematopoietic cell lines.conclusion: This EMH case is a response to chronic hypoxia rather than to a bone marrow lesion as it has usually been described.