It sounds like the premise of a science-fiction movie or book, but this story is the reality for one man living in Washington who curiously took a paternity test after his newborn baby’s blood type matched neither his own nor his wife’s. The 34-year-old man grew nervous because the couple had gone through a fertility clinic to aid his wife in getting pregnant and they feared that sperm samples had been mixed up in the process.
As a result, he returned to the clinic and took an initial paternity test that he subsequently failed. To take it a step further, they decided to administer a genetic ancestry test which determined that this man was not the son’s father, but instead he was his uncle. Since the man has no brothers, it seemed impossible that his son could actually be the offspring of a sibling, and that’s when geneticists took it a step further.
The man’s sperm was found to have a 10 percent match to the genes of the infant, and when geneticists cross-matched the man’s sperm with his saliva, they realized what the problem was: the man is one of the rare human chimeras in the world
“Even geneticists are blown away by this,” Barry Starr, a geneticist at Stanford University, told BuzzFeed News.
A human chimera is a person composed of a genetically distinct types of cells. Geneticists concluded that the sperm from the man must be the DNA that the man absorbed in the womb from an unborn twin brother. While human chimeras are rare, multiple pregnancies that result in only a single birth are not. It’s estimated that 1 in 8 single childbirths actually start off as multiple pregnancies, so it’s fairly common for women to be pregnant with multiple fetuses in the beginning and never know it. What’s not common is the single child absorbing that DNA when one of the fetuses doesn’t make it.
Starr worked specifically with the couple after their first failed attempts and says that the moment the man was shown to be the son’s uncle was a “eureka moment.” This is the first reported case of a paternity test being fooled by a human chimera, and now doctors aren’t sure what to make of this very obvious loophole in testing. Since most tests rely on cheek swabs, and the man failed this test outright, it’s unknown how many others have failed for similar reasons.
Some other similar cases that involve human chimeras occurred in 2002 and 2006. In 2002, a woman was in need of a kidney transplant and her two sons underwent testing to see if they could be donors. The results said that the two young men were not even the sons of this woman, which of course led to further questioning. In the end, it turns out that this woman’s blood cells had one set of genes while her ovaries had another. In 2006, a woman found that she had the same problem, although it nearly caused her to lose her children after maternity tests required for welfare payments came back negative.
It’s surprising that this most recent Washington man is the first to be a human chimera whose genes failed the paternity test, but, according to the geneticists that worked with him, it’s not all that surprising when looking at the man. He has two-tone striped skin that is so distinct that he told his peers he was a burn victim when he was young to escape bullying. Doctors say that such a pattern is suggestive of chimerism.