DIRECT EVIDENCE FOR DISSOCIATED MEGAKARYOCYTIC CHIMERISM IN A WISKOTT-ALDRICH PATIENT SUCCESSFULLY ALLOGRAFTED

We report a Wiskott-Aldrich patient who underwent allogeneic bone marr ow transplantation from his HLA-identical sister at the age of 25. Con ditioning regimen consisted of cyclophosphamide (180mg/kg) and thoraco -abdominal irradiation (6 Grays). Cytogenetic follow-up revealed rapid and complete lymphoid chimaerism, but prolonged mixed bone marrow chi maerism. Correlative interphase cytogenetics performed on bone marrow smears using dual-colour fluorescence in situ hybridization with X and Y specific probes showed that the proportion of donor cells was signi ficantly higher within megakaryocytes than in other lineages, This pat ient therefore presented with dissociated lineage engraftment, which i s not exceptional in congenital diseases and aplastic anaemia, but has not previously been described in Wiskott-Aldrich syndrome. Bone marro w transplantation was successful despite this delayed engraftment whic h ensured adequate production in the involved cell lines.