Grzegorz Helbig1, Sławomira Kyrcz-Krzemień2. 1. Department of Hematology and Bone Marrow Transplantation, Silesian Medical University, Katowice, Poland. Electronic address: ghelbig@o2.pl. 2. Department of Hematology and Bone Marrow Transplantation, Silesian Medical University, Katowice, Poland.