The Scianna blood antigen system consists of seven antigens.
[1][2] These include two high frequency antigens Sc1 and Sc3, and two low frequency antigens Sc2 and Sc4.
[1] The very rare null phenotype is characterised by the absence of Sc1, Sc2 and Sc3.
[1] The antigens are caused by changes in the erythroid membrane associated protein (ERMAP).
[3][4] This blood group system was discovered in 1962 when a high frequency antigen was detected in a young woman (Ms. Scianna) who had experienced several late pregnancy losses due to haemolytic disease of the fetus.