Loss of mismatched HLA in acute myeloid leukemia relapse after haploidentical peripheral blood stem cell transplantation combined with unrelated cord blood: A case report

Mismatched human leukocyte antigen (HLA) loss is an essential mechanism involved in immune escape and recurrence in acute leukemia after haploidentical transplantation. Patients relapsing after transplantation with HLA loss have a poor prognosis, and are less likely to benefit from donor lymphocyte infusion (DLI) from the original donor. Here, we report a patient with high-risk acute myeloid leukemia who relapsed within six months after haploidentical peripheral blood stem cell transplantation (PBSCT) combined with unrelated umbilical cord blood (UCB) with a session of prophylactic DLI. This patient achieved transient remission after subsequent Interferon-α-1b treatment for two weeks but experienced a second relapse within one month. Genomic analysis by real-time PCR assay revealed that this patient had a loss of an entire mismatched HLA haplotype that was derived from her haploidentical donor. Haploidentical peripheral blood stem cell transplantation with prophylactic DLI might be a triggering event for HLA loss relapse after haploidentical transplantation combined with UCB. HLA loss should be considered in patients with post-HSCT relapse, especially in haploidentical transplantation.