SPONTANEOUS RH AND ABO TYPE CHANGES AS AN EARLY SIGN OF LOSS OF HETEROZYGOSITY IN ACUTE MYELOID LEUKEMIA

Background: Loss of heterozygosity (LOH) is a form of allelic imbalance by which a heterozygous somatic cell becomes homozygous because one of the two alleles is lost. LOH is a rare phenomenon that is sometimes seen in patients with acute myeloid leukemia, where it can sometimes precede the detection of blasts in the peripheral blood. We report two patients with LOH preceding and suggesting the diagnosis of AML.

Case One: GM, caucasian female, 76 years old. In our laboratory, inconsistent results were detected in serological RhD and RhE typing with different anti-D and anti-E reagents. Genotyping was performed. No RHD variants were detected and there was a reduced signal for RHE; using sequencing, we found no changes in RHD exons 1 to 10. The result was negative for RHD exon 3 duplication. Therefore, the conclusions were as follows: RHD hemizygote, with no RHD changes.

Case Two: DM, caucasian female, 78 years old (A ccdee kk), Polycythaemia Vera. A prevalent population of group O RBC with a residual RBC population reactive with anti-A was observed, and anti-B isoagglutinin was present. The patient’s genotyping was ABO*O.01;A.01. The clinical findings suggested an evolution towards acute leukaemia.

Methods: Blood group phenotypes were evaluated using a microcolumn agglutination assay and automatic high-productivity analysers supplied by Grifols. RHD an RHCE genotyping were performed using the Immucor BioArray RHD/RHCE BeadChip^TM. Genotyping for ABO was performed using an ERY Q ABO supplied by BAG Diagnostics.

Conclusions: Few reports have been published on weak expression of D antigen in serological RhD typing due to LOH in AML, and even fewer on weak expression of other Rh antigens. Reports concerning ABO LOH are slightly more common. In both of the reported patients, LOH was observed early together with a shift to an acute myeloid leukaemia.