Blood Group: MNS
Common: 45% Caucasians, 69% Blacks are at risk for developing anti-S.
Causes HDN: Yes
Critical Titer: 1:16
Anti-S is more common than anti-s, but both can cause severe HDN . Anti-S is capable of causing rapid red blood cell destruction .
Anti-S can be naturally occurring . Because anti-S is naturally occurring, the father needs to be tested for the S antigen. It is possible that both parents could be negative for S, in which case, the anti-S would be naturally occurring and would not harm the baby because the baby would be negative for S like both parents.
Anti-S that is not naturally occurring, but that occurs because of blood mixing, can be fatal . In 1952 there were two examples of anti-S causing HDN, one of which was fatal . Despite the potential to be very severe, anti-S is not always fatal. An infant with anti-S experienced a hematocrit drop and rise in bilirubin but required no treatment .
1 - https://www.ncbi.nlm.nih.gov/books/NBK2274/
2 - http://onlinelibrary.wiley.com/doi/10.1111/j.1423-0410.1958.tb03599.x/full
3 - http://www.bloodjournal.org/content/7/10/1030.short?sso-checked=true
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2640537/
5 - http://onlinelibrary.wiley.com/doi/10.1111/j.1423-0410.1995.tb01681.x/full
6 - http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2257.1990.tb01117.x/full