[1] Univ Helsinki, Dept Med Genet, Helsinki, Finland
[2] Univ Helsinki, Cent Hosp, HUSLAB, Helsinki, Finland
[3] Univ Helsinki, Cent Hosp, Dept Clin Genet, Helsinki, Finland
[4] St Marys Hosp, Dept Haematol, London, England
[5] Ctr Hosp Cote Basque, Serv Hematol, Bayonne, France