Anti-M

Blood Group: MNS

Common: 21% of caucasians and 25% of blacks are M- and at risk of developing anti-M

Causes HDN: Yes
Critical Titer: 1:16
Information:
Anti-M can be naturally occurring, but may be developed in response to blood mixing [1]. This makes it important to determine the M antigen status of the father. Anti-M can run the gamut of needing no intervention after birth to needing transfusions, exchange transfusions, and dealing with lasting anemia [2, 5, 6]. Anti-M can also cause delayed onset anemia [10]. One woman reported repeated stillbirths due to anti-M [4]. After an affected pregnancy, IVIG and plasmapheresis can be done during pregnancy [6].


M antigens are found on the surface of the cells that will become RBCs, so anti-M will destroy the progenitor cells before they even turn into red blood cells. Because the RBC precursors (the progenitor cells) do not have hemoglobin, less bilirubin is released. Less bilirubin being released means that jaundice can be less common in infants, but the underlying anemia may still be severe. [3, 6]  


Anti-M can also have a negative DAT but baby still be severely affected [3, 6, 13, 14, 15]. 


Articles:

1 - https://www.ncbi.nlm.nih.gov/books/NBK2274/

2 - https://www.ncbi.nlm.nih.gov/pubmed/7625079

3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2672780/

4 - https://www.ncbi.nlm.nih.gov/pubmed/7195138

5 - https://www.ncbi.nlm.nih.gov/pubmed/2638542

6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4339947/

7 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4339943/
8 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4140072/

9 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2798772/

10 - https://www.ncbi.nlm.nih.gov/pubmed/24262303

11 - http://onlinelibrary.wiley.com/doi/10.1111/j.1423-0410.1995.tb03927.x/full

12 - https://www.ncbi.nlm.nih.gov/pubmed/9397112

13 - http://www.ajts.org/article.asp?issn=0973-6247%3Byear%3D2015%3Bvolume%3D9%3Bissue%3D1%3Bspage%3D98%3Bepage%3D101%3Baulast%3DArora

14 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4006517/

15 - https://www.ncbi.nlm.nih.gov/pubmed/2771305