Anomalous expression of the Rh antigen, D, has occasionally been observed in patients with certain myeloproliferative disorders. Indeed, this phenomenon led to the tentative assignment of RH to the short arm of chromosome 1. PCR-based analyses were performed on DNA from an 82-year-old D+ Caucasian patient with chronic myeloid leukemia after her RBCs became D–. For nearly 7 years, the patient’s RBCs typed as strongly D+, but in March 2006, they typed weakly D+ and in August 2006 typed D– by both direct hemagglutination and the IAT. The D– typing persisted until the patient’s death in September 2006. To study the underlying cause of the change in D type, PCR-based assays were performed on DNA extracted from peripheral WBCs from the patient’s sample collected in August 2006. No amplification was obtained using primers designed to amplify RHD exons 5, 8, or 10, and intron 4. Very weak amplification was obtained using primers designed to amplify RHD exons 3, 4, or 7. Two assays that detect the hybrid Rhesus box showed deletion of RHD. Amplification of RHCE in the patient’s DNA was as efficient as that of control samples, and multiplex and PCR-RFLP assays predicted her RBCs would be C–E–c+e+. Based on finding a hybrid Rhesus box and absence of D-specific exons, we conclude that DNA from the patient’s WBCs carries a deleted RHD. This explains the molecular mechanism underlying the change from D+ to D–. Immunohematology 2008;24:160–164.
