Blood Group: MNS

Common: Approximately 10% of the population is SS and capable of forming anti-s.

Causes HDN: Yes
Critical Titer: 1:16*
Anti-S is more common than anti-s, but both can cause severe HDN [1]. Although approximately 10% of the population is SS and capable of forming anti-s, there are very few examples. In one article, there were 3 examples of anti-s to date and the authors reported the fourth case which was fatal at 39 weeks. Despite this rarity, anti-s can be fatal. In all 3 examples, titers were only 1:8. In spite of low titer, anti-s is capable of rapid red blood cell destruction, causing severe HDN. [2] In another article, the infant had severe HDN and required 2 exchange transfusions [4]. In this 1972 article documenting mild HDN due to anti-s, the titer was 1:16, and the infant had a cord bilirubin of 3.0, yet was not treated [3]. Current practices would have put the infant under phototherapy lights.

*With multiple examples of anti-s causing issue at low titer, it begs the question of if 1:16 is the appropriate critical titer for this antibody.


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