RHD del28Phe (DMW) encoded by a novel in‐frame deletion resulting in reduced D antigen expression

The novel in‐frame deletion is associated with a considerably reduced expression of D antigen and a variant RhD phenotype. The mutation occurs in close proximity to the first exofacial loop of the protein which is mainly encoded by sequences of Exon 1. Structural changes caused by the deletion may reach the surface of the protein in this region. Consistent with the substantially weakened agglutination reactions observed with anti‐D LHM59/19, the presence of an altered Loop 1–dependent epitope 8.15 appears to be possible. Although all the anti‐Ds we used to examine the epitope pattern reacted positive with the proposita's RBCs, the presence of a qualitatively altered D antigen may not be excluded. The primigravida had not received prenatal or postnatal RhIG prophylaxis. Though pregnant with a D‐positive fetus, no immunization was observed; however, whether this novel D variant permits anti‐D immunization remains unclear. Hence, D‐negative transfusion in carriers and prophylactic use of RhIG in pregnancy is recommended. DMW expands the exceptionally rare RHD in‐frame deletions reported and should be regarded as a putative partial D allele.