Paravertebral extramedullary hematopoiesis associated with improvement of anemia in congenital dyserythropoietic anemia type II

Thoracic masses resulting from extramedullary hematopoiesis developed in two sisters of Moroccan origin with congenital dyserythropoietic anemia type II (HEMPAS). In one patient, the diagnosis of extramedullary hematopoiesis was confirmed histologically. The appearance of extramedullary foci of hematopoiesis mimicking mediastinal tumors has not been previously described in HEMPAS. These masses result from persistent erythropoietic stimulation associated with chronic hemolytic anemia. In both patients, detection of the asymptomatic masses was preceded by normalization of hemoglobin levels. Thus unexpected correction of a chronic refractory anemia associated with the appearance of mediastinal masses might be the heralding manifestation of an effective extramedullary hemopoiesis.