It is common knowledge that hematologic malignancies may lead to ABO discrepancies.1 In fact, case reports highlight that when a patient with hematologic malignancy shows relapse of disease after a bone marrow transplant, ABO discrepancy may be the first sign of graft failure.2 RhD discrepancy, on the other hand, is rarely associated with such conditions,3,4 and instead is often a result of a variant antigen expression. A case we followed recently at our institution challenged this presumption.5
The patient was a group A, D+ male in his 60s with a history of B-cell acute lymphoblastic leukemia (B-ALL) and allogeneic stem cell transplant from a group A, D+ female donor. The post-transplant period was uneventful until approximately 8 years later, when the patient was diagnosed with colon cancer. Following surgery, he received chemotherapy and shortly thereafter, he developed myelodysplastic syndrome (MDS). His D typing was consistently positive, as expected, given the group A, D+ identical donor. However, around the time of MDS diagnosis, he developed mixed-field reactivity for D antigen, and within a few weeks the D expression was completely abolished.
Following our standard operating procedure, a sample was sent to the immunohematology reference laboratory, which performed polymerase chain reaction (PCR) testing, but did not identify any RHD variants. Subsequent testing at a different reference lab using Sanger sequencing confirmed the presence of an RHD gene. Based on expert recommendation, microarray testing was performed in-house and revealed deletions involving the RHD locus in female cells originating from the stem cell donor. The etiology of the discrepancy was found: mutation at the gene level due to MDS.
In the meantime, the patient was evaluated and prepared for a (second) stem cell transplant. His donor this time was a group AB, D+ male; and D antigen started showing strong presence (4+) after the transplant. In the short-term follow-up, the genetic abnormalities encompassing the RHD region were still detectable by fluorescence in situ hybridization (FISH). Eventually, in about a year, FISH showed full engraftment. The patient’s D typing remained consistently positive after this second transplant despite the presence of mutations in the cells from the first donor in the early days of the post-transplant period.
It is worth mentioning that initial considerations included RHAG mutations as the patient had rare spherocytes. Knowing that loss of RhAG would lead to decreased RhD and RhCE antigen expressions, the patient was serotyped and found to be positive for c (little c) and e (little e) antigens, making RhAG-related causes unlikely. Later, microarray testing confirmed that the RHAG region was not affected.
When the literature was reviewed on loss of RhD, a case report by Chow et al3 of acute myeloid leukemia (AML) with loss-of-heterozygosity mutations encompassing the RHD region in the patient’s own bone marrow cells was found. Another case report, by Murdock et al,4 mentioned a patient with chronic myeloid leukemia (CML) who had deletion of the RHD gene in the patient’s white cells.
Review of the literature along with this case led to three conclusions. (1) While D antigen, like ABO, may be lost in hematological malignancies, the loss usually happens very late in the disease course. (2) It can be proposed that RhD expression is markedly more stable than ABO; the presence of some healthy cells – in this case, from the second donor – was sufficient to keep strong RhD expression despite having mutated cells from the first donor in the early post-transplant period. (3) Comparing the case by Murdock et al to our case, it is seen that that loss of RhD can be caused by a deletion in the RHD gene or the deletion of the entire gene.
Finally, it is imperative to understand and utilize different testing modalities to resolve a discrepancy.
References
1. Chenna D, Mohan G, Reddy VR, Shastry S. The disappearance of blood group antigens: a clue to the clinical diagnosis of leukemia. Transfus Apher Sci 2019;58:48–9. doi:10.1016/j.transci.2018.11.010.
2. Yurtsever N, Lee ES, Pinatti L, Shah B, Tormey CA, Siddon AJ. Mixed-field ABO front typing as an early sign of disease recurrence in ABO-matched stem cell transplantation. Immunohematology 2024;40:89–92. doi:10.2478/immunohematology-2024-013.
3. Chow S, Pendergrast J, Ochoa-Garay G, et al. Mixed fields on RhD typing as an indication of loss of heterozygosity on chromosome 1p in acute myeloid leukemia. Leuk Lymphoma 2015;56:2196–9. doi:10.3109/10428194.2014.982641.
4. Murdock A, Assip D, Hue-Roye K, Lomas-Francis C, Hu Z, Vege S, Westhoff CM, Reid ME. RHD deletion in a patient with chronic myeloid leukemia. Immunohematology 2008;24:160-4. doi:10.21307/immunohematology-2019-291.
5. Yurtsever N, Carmichael G, Li P, Wen JD, Chai H, Diadamo A, Denomme G, Tormey C. Loss of D expression associated with hematologic disease progression: a case report and review of the literature. Immunohematology 2025;41:80-3. doi:10.2478/immunohematology-2025-012.
