"Weak D"

[janp]

We have a Mother with a "weak D". Her baby's cord blood also looks like a "weak D" .

What to do at this time?? Do they cancel out the need for Rhogam? I thought it safer to give Rhogam for Weak D with RH pos baby , but haven't had this problem before.

Any suggestions! Thanks, Jan and Rosanne

[Deny Morlino]

Follow my logic for a minute... donors are tested for weak D so the unit is "properly" called Rh positive. As they may have part of the D epitope, the possibility exists that the unit donated by a weak D donor could potentially cause a Rh negative recipient to form a partial Anti-D.

From a recipient stand point you would prefer a weak D patient to receive Rh negative blood. As they only have part of the D epitope exposure to the portion of the epitope they do not have may cause a partial anti-D to form.

Err on the side of caution and administer rhogam. If you think of the baby as a "donor" and mom as the "recipient" it is easier to follow. Hope this helps.

Edited June 3, 2010 by Deny Morlino
Clarification

[Deny Morlino]

Sorry! Forgot to say welcome to BBT JanP and Rosanne

[Malcolm Needs ☆]

Follow my logic for a minute... donors are tested for weak D so the unit is "properly" called Rh positive. As they may have part of the D epitope, the possibility exists that the unit donated by a weak D donor could potentially cause a Rh negative recipient to form a partial Anti-D.

From a recipient stand point you would prefer a weak D patient to receive Rh negative blood. As they only have part of the D epitope exposure to the portion of the epitope they do not have may cause a partial anti-D to form.

Err on the side of caution and administer rhogam. If you think of the baby as a "donor" and mom as the "recipient" it is easier to follow. Hope this helps.

I concur totally with both of Deny's posts (so welcome from me too).

The other thing that it is well to remember is that, although the mum may have a weak D, it could be a partial D, and although the baby may have a weak D, it could also be a partial D, BUT, it may be a different partial D to the mum's partial D, because it could have been inherited from the dad. Unlikely I know, but try convincing a judge and jury!

I, like Deny, would err on the side of caution and give the anti-D immunoglobulin prophylaxis.

:):):)

[janp]

Thanks for the input, sounds like a plan. I'll give the Rhogam to the Mom. Always harder to explain to the Doc what the results mean. Thanks, Jan and Rosanne

[donnalander]

Would you not have to perform a KHB to determine the extent of the fetal-maternal bleed (as the rosette testing would be positive)? Also, please correct me if my aged brain has failed me and I am wildly off base, wouldn't the RhIG attach to the maternal partial D? I don't see how this wouild provide any type of protection.

[tjohnk1]

We would give a dose of Rhogam based on results of the KHB. We just had one of these a couple weeks ago! We'd rather err on the side of caution and use the thinking Deny talked about.

[adiescast]

Would you not have to perform a KHB to determine the extent of the fetal-maternal bleed (as the rosette testing would be positive)? Also, please correct me if my aged brain has failed me and I am wildly off base, wouldn't the RhIG attach to the maternal partial D? I don't see how this wouild provide any type of protection.

I guess it depends on which part of the D antigen she is missing. If the RhIg attaches to maternal cells, then it would not protect her anyway, because it is directed against the part of the antigen she has (to which she would not make an antibody). But presumably in that circumstance, she would not make an anti-D anyway and the RhIg is superfluous.

I hope that makes sense...

[Yanxia]

IgG have the function of immunosuppression, If my memory don't treat me, it is when IgG Fab bind antigen and Fc bind B cells receptor , this can induce the immunosuppression to this kind of antigen.

[heathervaught]

Rh immune globulin is made from pooled human plasma - not monoclonal. So presumably, it is a blend of specificities.

If she is genetically weak D, then she can pass the gene on to her child. If the father does not pass a RHD gene to the child, then the "weak" gene from the mom is the only expression of D that the child has inherited. So presumably, the child's D expression should be identical to the mom's, and mom would not make anti-D. I suppose that it is also possible that the father passed along a "weak D" gene to the child...then the child would have two D expressions and then would potentially have a different epitope than the mom, which could prompt her to make anti-D.

I vote for give the prophylaxis. It seems that the benefits would outweigh the risks.

[Malcolm Needs ☆]

Rh immune globulin is made from pooled human plasma - not monoclonal. So presumably, it is a blend of specificities.

If she is genetically weak D, then she can pass the gene on to her child. If the father does not pass a RHD gene to the child, then the "weak" gene from the mom is the only expression of D that the child has inherited. So presumably, the child's D expression should be identical to the mom's, and mom would not make anti-D. I suppose that it is also possible that the father passed along a "weak D" gene to the child...then the child would have two D expressions and then would potentially have a different epitope than the mom, which could prompt her to make anti-D.

I vote for give the prophylaxis. It seems that the benefits would outweigh the risks.

Yep, that's what I meant in my earlier post. I would totally agree with your thinking.

In fact, we had a lady that we had to investigate not long ago that involved us having to send a sample to the IBGRL for molecular work, and it turned out that she was heterozygous for two different Partial D haplotypes and, of course, she was a baby once, and so her mum should have been given anti-D immunoglobulin when she was born (I don't know whether her mum was given this ir not).

:D:D:D:D

Edited June 15, 2010 by Malcolm Needs

[Mabel Adams]

Judd says "Whether RhIG will be beneficial in preventing D alloimmunization in women of a partial D phenotype has not been directly shown; however, no data indicate that it will not be effective. One could argue that most of the RhIG would bind to the D eiptiopes that are preseint on the maternal red cells; consequently, there would be insufficient RhIG available to prevent alloimmunization by fetal Rh-positive red cells and that more than the normal dose of RhIG may be required. However the exact mechanism by which RhIG prevents alloimmunization to D is still unknown, and so the need for the anti-D to be free in the plasma to prevent alloimmunization is a matter for conjecture." AABB Guidelines for Prenatal and Perinatal Immunohematology, 2005.

I agree with Shily's idea--the antibody will attach to the D antigen on its "front end" and the back end (Fc) will still be free to do the immunosuppression. Giving RhIG to ITP patients that are D positive is still immunosuppressive.

If you get into testing the father, then you also have to be sure the purported father is the actual genetic father. And don't forget the world of donor eggs and sperm.

[rravkin@aol.com]

I think it is important to understand that our testing system for weak D can only determine the presence or abscence of weak D and not the cause; ie. lack of expressed Ag or altered Ag (D mosiac). As such I would treat the mother as though she were Rh Neg and follow through with Rossett-testing (FMHS) and KHB to determine the number of vials of RhoGam needed. I definitely agree with erroring on the side of caution as I witnessed an L&D pt having been given RhoGam who did not appear to need it. The RhoGam was given because the patient's appearent historical RH type was Neg. When she was addmitted to our facility we resulted her as Rh pos and confirmed it. The reactivity we saw was approx 2+ to 3+ in strength. We found that the patient had received RhoGam approx 3 months earlier. It was amazing to see the RhoGam in action as it lowered the Rh reaction from, what would normally be 4+, to 2+ or 3+. The patient physician was notified and also desided to error on the side of caution and follow through with RhoGam post delivery.