TRANSPLANTED SICKLE-CELL DISEASE PATIENTS WITH AUTOLOGOUS BONE-MARROW RECOVERY AFTER GRAFT FAILURE DEVELOP INCREASED LEVELS OF FETAL HEMOGLOBIN WHICH CORRECTS DISEASE SEVERITY

Bone marrow transplantation (BMT) is the only curative therapy for sickle-cell disease (SCD), but is not devoid of failure risk. Nine patients with severe SCD were grafted in our institution between 1988 and 1993. Six patients successfully engrafted, but three failed to engraft and had delayed autologous recovery. All patients had, prior to BMT, low levels of fetal haemoglobin (HbF less than or equal to 3 . 5%). No change in HbF occurred in successfully grafted patients. In the three patients with graft failure HbF increased and remained persistently present at a high level (greater than or equal to 22%) 14 months, 16 months and 39 months post BMT, although two of the three patients were homozygous for either the Benin or the Central African Republic haplotype, a characteristic associated with low HbF level. Of interest, these three previously severely affected patients remain free of vaso-occlusive events. The mechanism responsible for the expression of high levels of HbF in our three patients with graft failure is not understood, but it protects them from the recurrence of severe vaso-occlusive crises.