The aim of the first study was to determine the effect of pretransplantationhyperferritinemia on survival, graft versus host disease(GVHD). It was found that hyperferritinemia was associated withdecreased frequency of chronic GVHD, shorter survival and higherrisk of relapse. In the second survey we evaluated sigificance ofhyperferritinemia in patients with Gaucher disease (GD1). Studyshowed elevated ferritin levels in the majority of patients There wasno correlation between hyperferritinemia and the clinical status. sIL-2Rα was relatively low. TNF-α was moderately elevated.Hiperferritinemia improved and TNF-α normalized in all treatedpatients. In the third study we analyzed significance ofhiperferritinemia in the malignancy associated hemophagocyticlymphohistiocytosis (M-HLH). We have found elevated ferritin,cytokine and sIL-2Rα levels. Based on the existing literature data aswell as on the results presented in the submitted thesis, it can beassumed that ferritin can be used as a prognostic biomarker in patientstreated with alloSCT and as a marker of treatment response in patientswith GD1. Level od ferritinemia had no prognostic significance inpatients with M-HLH.