In 1953 a human chimera was reported in the British Medical Journal. A woman was found to have blood containing two different blood types. Apparently this resulted from her twin brother’s cells living in her body. A 1996 study found that such blood group chimerism is not rare.
Chimerism is a condition whereby a person has not one but two complete genomes (sets of DNA) in their body. One genome is found in one region or organ(s), while the other genome can be predominant in other organs or tissues.
This is from Mixed field reactions in ABO and Rh typing chimerism likely resulting from twin haematopoiesis:
In conclusion, this case identified a case of a permanent genetic chimera resulting from twin-twin exchange of genetic material in utero. Suspicion for the presence of a chimera was initially prompted by the findings of an ABO and Rh discrepancy on a routine pre-transfusion sample. Additional questioning uncovered the existence of a deceased twin. Further characterization of the discrepancy was achieved in a reference laboratory, including a demonstration of the use of flow cytometry to delineate and quantify the presence of two distinct cell populations.
What is also more common than previously known of is a vanishing twin syndrome. One consumes all of the resources usually and the other weaker one dies. A sense of survivor’s guilt is what many surviving twins feel for a reason.
Have you ever noticed how so many celebrities and those who can afford excellent health care tend to have a lot of twins?
Of the 4 major reasons why blood type tests can show different results, chimerism is at the lower end. Human error is the main reason.
If you or someone you know has this phenomenon, feel free to comment.
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They say those of us who are left handed may have been a twin early in pregnancy. My oldest daughter who is a lefty has had depression for years and one reason could be because she seen an early ultrasound of about 5 weeks, there’s clearly 2 sacs; one on the left, and one on the right of my uterus. The next ultrasound at 8 weeks they only seen one. This really affects her even though I’ve tried to tell her it’s a natural part of pregnancy.
Thank you for sharing this, Stacy.
The truth is that many of us are surviving twins and don’t even know it. If it’s any comfort, it is a part of nature that the stronger survive. In a sense it also may avoid future issues as life IS tough. It is sad and makes me sad to hear. But there is definitely nothing that she “should have done differently”. 🙂 She acted based on genetic predisposition. The same ones that help her survive in today’s world.
Mike
No your bone marrow dictates this. You can have two different DNA
Which is called “chimerism”: Having two sets of DNA.
Hi, I got a DNA test last year through My Heritage. The raw profile shows my two X chromosomes and a partial Y chromosome with lots of gaps and long rows of genomes. I only learned about chimerism recently and never thought much about it. I’ve always had little quirks though. My index finger has an extra phalangeal line, I continue to have a brown area on my right green eye (used to be more pronounced as a teen), I have a slight birthmark on my arm and some of my toes are different from the “matching” toe. I honestly thought these things were the result of inbreeding until the DNA came back. I have tried to confirm chimerism with an expert – no such luck. Chromosome analysis is $5,000 and they won’t do a manual smear for me on a blood test, even after explaining the situation. Confirmation would be nice if anyone has some expertise on here. I contacted genetic counselors and they just tell me that’s not their “area”. Well, of course it isn’t! One more thing, I may have Hirschsprung’s disease, a condition that results in the third week of gestation. I have no idea if it’s related to the chimerism, like if that’s the week I absorbed a twin brother. Thanks for reading.