It is also the most polymorphic of the blood groups, with variations due to deletions, gene conversions, and missense mutations.

The classification of Rh-positive and Rh-negative individuals is determined by the presence or absence of the highly immunogenic RhD protein on the surface of erythrocytes.

[6] A recent study in the population of the island of Sardinia shows the association of a noncoding variant in the RHCE gene (rs630337) with an increased erythrocyte sedimentation rate(ESR).

This suggest a possible causal effect of this polymorphism on this inflammatory marker despite not found in coding region of the gene.

[7] This article incorporates text from the United States National Library of Medicine, which is in the public domain.