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Sonya Martinez

Newborn with naturally occurring anti-M?

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We have a newborn (2 hour old when the sample was collected from the patient) term infant who's mom is confirmed to have anti-E and anti-c.  Being a children's hospital we have specimens collected on all our patients and do not use the mother's sample.  Our workup shows the anti-E but instead of the anti-c we have a confirmed cold anti-M that reacts in gel and only at RT in LISS (tube method) and shows dosage.  We do 3 homozygous cells to rule in and out each antibody.  We completed a back type on the patient just to see and the patient has a  4+ reaction with A cells and negative with B cells (he's type O).  DAT IgG by gel is 2+ (not surprising).  We will be giving the baby E negative and c negative (since mom has it) crossmatch compatible units.  Has anyone else ever seen a newborn with a naturally occurring cold anti-M?

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Two things.  Firstly, although the anti-M may be "naturally occurring", it need not necessarily be IgM.  Many examples of anti-M, reacting in the cold and RT are, in fact, agglutinating IgG (a bit like ABO IgG antibodies and anti-P in the DL Test).  In addition, maternal IgG antibodies are actively transported across the placenta and, as a result, the baby ends up with a higher concentration of some IgG specificities in their circulation than is in the mother at birth.  As the anti-M in the baby's circulation is so weak (showing dosage), it could be that it is of maternal origin, but that it is so weak now in the mother that it is undetectable in her plasma using normal serological techniques.

Secondly, some precocious babies are (rarely) known to produce their own IgM antibodies at birth (this can be proved by the babies producing an ABO antibody that cannot have come from the mother - say a group O baby with anti-B in the plasma, from a group B mother, or by looking at the Gm and/or Km types of the immunoglobulins - see, for example, Toivanen P, Hirvonen T.  Iso- and heteroagglutinins in human fetal and neonatal sera.  Scand J Haemat. 1969; 6: 42-48), so it could be the baby's own antibody, despite what I said above!

Lastly, and this came to me as I was typing (hence a third point), is the mother of the baby of Japanese origin?  The only reason I ask is that, if she is, be a bit careful, as anti-M of low titre has been known to cause a sort of delayed HDFN in this ethnicity (see Yasuda H, Ohto H, Nollet KE, Kawabata K, Saito S, Yagi Y, Neggishi Y, Ishida A.  Hemolytic disease of the fetus and newborn with late-onset anemia due to anti-M:  a case report and review of the Japanese literature.  Transfusion Medicine Reviews 2014; 28: 1-6.  doi: 10.1016/j.tmrv.2013.10.002).

Incidentally, although I have seen anti-A or anti-B in a newborn's plasma, I have never seen an anti-M.

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Malcolm Needs - Thanks so much for the quick response.  There's no ethnicity on the patient yet but I doubt she is Japanese by her last names (very Hispanic).  We are not planning on antigen typing the red cells for M at this point since it only showed up at immediate spin.  We didn't do the workup on the mom so although the other BB said they ruled M out we don't know for sure if they use the 3/3 homozygous rule that we use.  You are definitely correct about the M still possibly being IgG, I do realize, thanks for correcting me.  It's been a very weird year, since last July when we had our first true anti-U, then an huge increase in the number of extremely strong WAA, an anti-hrB at Christmas, and now this newborn.  I hope this doesn't become standard for us but with our Hematology/Oncology clinic growing each year and all the solid organ and HPC transplants I'm sure we're only touching the surface.  I miss the days when a children's hospital blood bank worried more about making smaller aliquots than dealing with rare antibodies.

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