[1] Univ Tor Vergata, Rome, Italy
[2] Univ Hosp Ulm, Ulm, Germany
[3] Univ Palermo, Div Hematol, Palermo, Italy
[4] Univ Catania, Div Hematol, Catania, Italy
[5] Univ Milan, Osped San Raffaele, Unita Ematol, I-20127 Milan, Italy
[6] Hosp Gen Castellon, Hematol Serv, Valencia, Spain
[7] Kings Coll London, Dept Med & Mol Genet, London WC2R 2LS, England