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- Title
P36 A Novel RhD Variant.
- Authors
Tilley, L.; Bullock, T.; Mason, R.; Poole, J.; Daniels, G.
- Abstract
Introduction Variants of the RhD antigen are often categorised into weak D and partial D phenotypes, although the distinction between the two groups is unclear. One frequently used definition is the ability to make alloanti-D in partial D, but not in weak D phenotypes, however some phenotypes characterised as weak D are now known to be associated with alloanti-D production. On a molecular level, weak D phenotypes usually possess RHD mutations encoding amino acid subsitutions within the cytoplasmic or membrane spanning regions of RhD, whilst partial D phenotypes result from changes in the extracellular loops. Thus, weak D red cells could be regarded as having all epitopes of D, but expressed weakly, whilst partial D cells lack some D epitopes. We investigated the red cells of a black pregnant woman because of aberrant reactions obtained in routine D typing, in order to decide if prophylactic anti-D should be given. Methods Routine anti-D sera and a reagent anti-D panel were tested serologically by their recommended techniques. Genomic DNA was extracted from whole blood and subjected to sequencing of exons 1 to 9 of the RHD gene. Results and treatment The Rh phenotype of the patient was C- c+, E-, e+, V+, VS+. Anti-D reagents gave variable reactions and a novel pattern of reactions was seen with an anti-D panel. Sequencing analysis revealed a single G>A mutation at position 490, within exon 4 of the RHD gene, resulting in an Aspartate to Asparagine change at position 164 of the RhD protein (D164N). This appears to be a novel RHD mutation. The patient received prophylactic anti-D antenatally and at delivery. The maternal antibody screen and Kliehauer screen were negative and she delivered a full term D+ DAT negative infant. Conclusions A novel D variant has been identified with an D164N mutation, predicted to lie within the third extracellular loop of the RhD protein. We propose to call this D variant DDN. The molecular basis of this novel phenotype suggests that this could be categorised as a partial D , as the mutation results in a loss of D epitopes. This would be expected to result in the ability to produce alloanti-D although alloanti-D production was not reported in this case.
- Subjects
BLOOD transfusion
- Publication
Transfusion Medicine, 2006, Vol 16, p40
- ISSN
0958-7578
- Publication type
Abstract
- DOI
10.1111/j.1365-3148.2006.00694_36.x