Interesting Rh phenotype

[cbaldwin]

I just finished a two-week rotation at an IRL for school. The reference lab had a case that phenotyped as D- - . The genotype performed at a DNA lab was R¹R¹. The patient was from Turkey. The genotype of both of her parents was R¹R¹ and their phenotype was R₁R₁, as were the genotypes and phenotype of 4 of her 5 siblings. She had one sibling that had a genotype of R¹R¹ and a phenotype of D--.

There were a few cells left, and my instructor had me adsorb anti-C and anti-e from human plasma, elute it, and test for anti-C and anti-e. The results were weakly positive, very weakly positive.

I was just thinking that maybe we should have also treated the cells with ficin—that would have enhanced the reaction of C and e. And I also wondered: when a sample tests serologically as D- -, wouldn't a natural next step be to treat the cells with ficin since ficin enhances Rh antigens?

Could this be Rh32, the “R double bar N”?

Also, what is the DBT phenotype? Is that a partial D phenotype with a weak expression of C and e? I read that when Rh32 occurs in Caucasians, it is the DBT phenotype.

Would this patient be capable of making anti-C and anti-e, and if it is the DBT phenotype could she also make anti-D? I think the answers to these questions are yes.

What would be transfusion recommendations if she needed blood? I think maybe she should donate blood for herself and have it frozen in case she needs it.

I am a student, but these are not exam questions or questions from an exercise. They are questions that arose when I came home and started reading about D- - and Rh32.

Thank you!

[Rh-fan]

Nice case.

The fact that you see weak expression of C and e makes that this is not a -D- phenotype, maybe it is a .D. phenotype (weak expression of RhCe antigens). This also fits more with the DNA results, mostly there is no C or e detectable at the DNA level (because of the presence of RHD exons in the RHCE gene).

I am not a big fan of enhancing antigen expression with enzyme treatment, it depends on the reagent you use if it is possible (your reagent must be suiteble for this methode, most are not).

The RN phenotype is mostly found in people of africa origin (Turkey is close but not that close), but the serologic results do fit.

The Rh32 antigen in DBT is expressed on the RhD antigen, while the Rh32 antigen in the RN phenotype is expressed on the RhCe protein. So this dous not fit with DBT (has normal C expression). DBT can make anti D, but I do not think that this patient has a DBT variant and will make anti D.

Formation of anti C and e can be possible. But alslong as these are not present I would not recomend the transfusion of -D-. At this moment I would select donors that are R1R1 (no anti c and E formation), but autoloog is always oke.

You will need to do more investigations (DNA and serological) for a definitive transfusion advice.

Peter

[galvania]

Hmmmm. I wonder....A couple of years ago a lab in the Ticino (Italian-speaking part of Switzerland) called me in a panic because they had a D--. The woman could never be fully investigated because she went back to Turkey, which is where she came from.......Wonder if they're related.

[cbaldwin]

Yes, this family still lives in Turkey! One daughter lives in the US near the Reference lab where I did my 2 week rotation.

After the Reference Lab did the workup on this patient and she was told she had an interesting phenotype, she said she would arrange to obtain specimens from her family in Turkey. A cousin of the family in Turkey is a physician and arranged to have everyone drawn and the samples were FedEx'd to the Reference lab.

They saved a little bit of sample for me so I could practice, so that was my part of it.

When I got home from my 2 week sojourn I started reading whatever I could about D-- and am trying to make sense out of it all.

Thank you Peter for your feedback! I would like to understand the Rh system better!

[cbaldwin]

Thank you Peter for this information. I am reading in the Antigen Facts Book that RH48, JAL, has a strong expression of D and weak expressions of C and e in Caucasians. (In Blacks there is a weak expression of c)

What is the difference between R₁R₁ with a weak expression of C and e and JAL? Are these two phenotypically similar but molecularly dissimilar? Can you test for JAL molecularly?

I'm a little confused and hope my questions make sense!

Edited August 7, 2012 by cbaldwin

[Rh-fan]

There are several phenotypes with a weakend expression of C and e. And the JAL+ phenotype is one of them, although I do not think that in the JAL+ phenotype the expression is so weak that the antigens are only detectable with absorption elution (as in your case).

The presence of a JAL+ phenotype can be tested with a (rare) anti JAL sera, but also on a moleculair level. The easiest way to determine what is causing the weakend expression is to (let) perform a full sequence of the RHCE gene. There are not a lot labs doing these tests. I know the NYBC is doing it.

Peter

[cbaldwin]

Thank you! They have sent the specimen for DNA sequencing. It was a good case to be exposed to because I got to do the adsorption/elution and it forced me to read more about the RH system.