176-P

Abstract

All stem cell recipients have their own story, each one being more complicated than others. We report here the case of an 18 year old female who developed an acute lymphoblastic leukemia 10 years ago and went through many stem cell grafts. Complications in HLA typing due to chimerisms had to be addressed in an unconventional way. The HLA-A, -B, -C and -DRB1 were analysed in 2002 using serological methods and SSO low resolution and DRB1 and DQB1 were also analysed in high resolution by SSP. More than nine years after, the HLA-A, -B, -C, -DRB1 and -DQB1 were performed by sequencing, using PCR reactions of exons 2, 3 for loci A, B and DQB1, exon 2 for DRB1, exons 2, 3 and 4 for C and SSP. Blood sample, mouth swabs and hair follicles were used for DNA extraction and HLA typing. The patient was diagnosed with acute leukemia and Ph(+) in 2002. HLA typing was performed at low resolution for the related donor search. No sibling was compatible and the transplant team had to rapidly graft a 4/6 compatible cord blood unit. In 2008, the patient relapsed and received a second 4/6 compatible cord blood graft, using once again the HLA low resolution typing. Again, by the end of 2011, the patient relapsed and blood samples were sent to Hema-Quebec HLA lab to perform high resolution typing and start an unrelated donor search. The level of chimerism was interfering with the HLA typing of loci B, C, DRB1 and DQB1. The DNA extracted from mouth swabs was also chimeric. The unrelated donor search had to be initiated with high resolution HLA typing deduced from the parent’s inherited haplotypes. The patient’s typing still had to be confirmed and the only material left to do it was the hair follicles. Because this material is not routinely used in our lab, DNA extraction was performed by the Quebec forensic laboratory, allowing us to perform the high resolution confirmatory typing. An unrelated donor could be identified and the patient is now being prepared for her third stem cell graft.