Allogeneic HSCT strategy for adult HLH with RIC and incorporation of early (“distal”) administration of alemtuzumab. GVHD prophylaxis comprised calcineurin inhibitor (tacrolimus) along with methotrexate or sirolimus for HLA-matched donors and posttransplant cyclophosphamide along with tacrolimus and mycophenolate mofetil for haploidentical donors. Alemtuzumab was administered at a median of 25 days before stem cell infusion.