Prevalence of rhesus phenotypes among local population in Karachi.

The Rhesus (Rh) blood group system is one of the most complex systems. Over 46 different antigens have been serologically defined. Rh antigens are associated with the red cell membrane and are considered important fortheir integrity. The genes for Rh antigens are encoded together on the short arm of chromosome. One gene codes for Rh D antigen while the other gene encodes the polypeptide carrying the Rh C/c as well as Rh E/e polymorphism. The absence of the entire or atleast part of the Rh D gene causes Rh D negative phenotype. The Rh blood group system is the second most important in blood transfusion after ABO blood group system. The Rh system is involved in the haemolytic disease of the newborn, haemolytic transfusion reaction and in autoimmune haemolytic anaemia and in forensic work. Among Rh antigens, Rh D, C/c and Etc antigens are most important. In a given population, it is important to know the frequency of different Rh antigens because of its clinical significance. In Caucasians, Rh D is present on the red cells of 85°A of the population. In the Orient, almost 100% of the population are Rh D positive. In Pakistan, though ABO and Rh D frequency has been worked out in last 20 years but Rhesus phenotype has not been well characterized. Rh phenotypes are elucidated in this brief report.