[1] Royal Free Hosp, Dept Dermatol, London NW3 2QG, England
[2] Ruhr Univ Bochum, Dept Dermatol, D-4630 Bochum, Germany
[3] Univ Mainz, Dept Pediat, D-6500 Mainz, Germany
[4] Royal Free Hosp, Dept Haematol, London NW3 2QG, England
[5] UCSC, Inst Pediat Clin, Rome, Italy
[6] Univ Zurich Hosp, Dept Med, CH-8091 Zurich, Switzerland