The authors present an account of an investigation of a female patient with dyserythropoietic anaemia type II (HEMPAS). On the plain film of the chest a defined shadow was detected in the posterior mediastinum. CT and MR examinations of the chest were performed. The conclusions of the above examinations were supplemented by needle biopsy which confirmed the diagnosis of extramedullary haematopoiesis (EMH). After intense treatment of the patient incl. splenectomy a folow up examinations were made to evaluate the therapeutic effect. Most useful for assessment of the activity of residual mediastinal tissue was examination by magnetic resonance which confirmed the fatty conversion of EMH foci. In the discussion the authors summarize the pathogenesis of extramedullary haematopoiesis, the differential diagnosis, possible complications and treatment.

        Key words: extramedullary haematopoiesis – mediastinum – anaemia – magnetic resonance