Haploidentical Bone Marrow Stem Cell Transplantation in Patients With Multiple Myeloma

Inclusion Criteria: * Patients with MM \<60 years. * Poor prognosis MM patients, permissive for KIR-ligand mismatch and with a KIR-ligand mismatched haploidentical donor. Poor prognosis is based on: * Patients with early disease recurrence (within 12 months after first ASCT) or * Patients after a minimum of three lines of chemotherapy (including high dose therapy followed by ASCT rescue therapy) or * Poor risk based on the cytogenetic profile. * Written informed consent * No HLA identical related or 10/10 matched unrelated donor * Permissive for KIR-ligand mismatch * Responsive after reinduction therapy * Measurable disease Exclusion Criteria: * \- Patients with an full matched (10/10) donor, who will enroll in the HOVON 96 study * Active uncontrolled infections * Uncontrolled CNS involvement by the malignant disease * Severe cardiovascular disease (arrhythmias requiring chronic treatment, congestive heart failure or symptomatic ischemic heart disease) * Severe pulmonary dysfunction (CTCAE grade III-IV) * Severe neurological or psychiatric disease * Significant hepatic dysfunction (serum bilirubin or transaminases ≥ 3 times upper limit of normal) * Significant renal dysfunction (creatinine clearance \< 30 ml/min after rehydration) * History of active malignancy during the past 5 years with the exception of basal carcinoma of the skin or stage 0 cervical carcinoma * Any psychological, familial, lingual, sociological and geographical condition potentially hampering compliance with the study protocol and follow-up schedule * Breast-feeding female patients. * Concurrent severe and/or uncontrolled medical condition (DM, hypertension, cancer).