Rhpositiv

Rhpositiv, also written Rh-positive, refers to individuals whose red blood cells express the D antigen of the Rh blood group system. The presence of the D antigen distinguishes Rh-positive from Rh-negative blood groups and is routinely tested in blood typing and prenatal screening. Rhpositiv individuals comprise the majority of the population, with prevalence varying by ethnicity.

Genetics: The D antigen is encoded by the RHD gene. If the gene is present and expressed, the phenotype is Rh-positive; if the gene is deleted or inactivated, the phenotype is Rh-negative. Inheritance is determined by the presence or absence of a functional RHD allele: individuals with at least one functional allele are Rh-positive, while those with two nonfunctional alleles are Rh-negative.

Clinical significance: Rh incompatibility between an Rh-negative recipient and an Rh-positive donor can cause transfusion reactions if appropriate matching is not performed. In pregnancy, Rh incompatibility can lead to hemolytic disease of the fetus and newborn (HDFN) when an Rh-negative mother carries an Rh-positive fetus; management includes Rh immunoglobulin prophylaxis and careful prenatal care. Anti-D antibodies can form after exposure to Rh-positive cells and can affect subsequent pregnancies.

Testing and prevalence: Serologic testing detects the D antigen; genotyping can determine RHD gene status. The prevalence of Rh-positivity varies by region; roughly 85% of people are Rh-positive in many populations, while Rh-negative frequencies are higher in Northern European ancestry and lower in East Asian populations.

History: The Rh system was discovered in 1940 by Karl Landsteiner and Alexander S. Wiener; the name Rh derives from studies in rhesus monkeys.