Extramedullary hematopoiesis in hereditary spherocytosis deficient in ankyrin: a case report.

Hereditary spherocytosis (HS) is a common inherited hemolytic anemia due to red cell membrane defects. Extramedullary hematopoiesis is a compensatory response to insufficient bone marrow blood cell production. The preferred sites of extramedullary hematopoietic involvement are the spleen, liver, and lymph nodes, but in HS the posterior paravertebral mediastinum is also commonly involved. A nonsplenectomized 74-year-old man with mild HS, with primary deficiency in ankyrin, was found by magnetic resonance imaging to have thoracic paravertebral hematopoietic masses. The patient showed high serum levels of erythropoietin, which may have played a role in the development of extramedullary hematopoietic masses through a continuous hematopoietic stimulus to erythroid cells in the propositus. The long-standing history of respiratory infections and of hypoxia in the propositus may have been an additional etiological factor.