On September 10, Donnie Heaton will celebrate his 21rst birthday. But unlike most 21-year-olds, Donnie weighs only 55 pounds. He is one of the oldest known individuals to have trisomy 18 (Edward syndrome). Each of his cells has an extra chromosome 18. One in about 6,000 newborns has the condition.
Trisomy 18 was in the news during the last presidential election because Rick Santorum’s young daughter Isabella has it. Her mom was 48 when she gave birth to Isabella in 2008; Donnie’s mom was 42 when he was born. The risk of producing an egg with an extra chromosome increases with maternal age.
I use a rather dire case to illustrate trisomy 18 in my human genetics textbook, a boy who died at age 22 days. And Google images pulls up photos of fetuses who never made it.
I’ve only encountered trisomy 18 a few times in genetic counseling, when the extra chromosome turned up with prenatal testing in women of “advanced maternal age” — over 35. Those cases ended with termination of pregnancy, either naturally or by choice. We called in a clergyperson for one case who candidly said he’d end the pregnancy, so bleak was the prognosis. In another case a couple had lost a child at 4 months, and the effect had been devastating on their then-preschooler, who lost his baby brother. Pregnant a third time, the couple wanted amniocentesis to avoid having another baby with the condition, although the empiric recurrence risk is only 1 in about 100.
A trisomy isn’t inherited; the extra chromosome is an accident of meiosis, a chromosome pair that doesn’t part as gametes form but instead overloads a fertilized egg. Technically this is called non-disjunction, and it just happens – it isn’t anyone’s fault.
Today, thanks to cell-free fetal DNA testing (aka non-invasive prenatal diagnosis), many patients can avoid the slight risk of amniocentesis and chorionic villus sampling and find out about the more common autosomal trisomies (13, 18, and 21). Fetal DNA floats around in the maternal circulation in pieces smaller than the mom-to-be’s, so it can be separated and compared. If chromosome 18 pieces outnumber pieces of other chromosomes by half, trisomy 18 is at hand.
The first two renditions of this type of test – Harmony and Materni-T became available in 2011, to a flurry of headlines. At the end of 2012, the American College of Obstetricians and Gynecologists gave the tests a thumbs-up, so far only for high-risk women who’d otherwise have more invasive testing. But further research may soon clear it for everyone. Shortly before that, DNA Science blog explained how pregnant women’s bloodstreams harbor fetal DNA.
Prenatal testing has become so pervasive that perhaps we lose sight of the fact that the detectable medical conditions are variable. Not all fetuses, newborns, and toddlers lose the battle with trisomy 18. Not everyone chooses to avoid the birth of a child with trisomy 18, and not everyone chooses prenatal diagnosis.Karen Heaton, Donnie’s mom, said no to prenatal testing. And her son, whom doctors predicted wouldn’t survive more than a few months, is about to turn 21. I read about Donnie in a terrific article in the Tampa Bay Times by staff writer Lane DeGregory, then spoke with Karen.
Donnie, at 21, is very much an exception. Half of fetuses with trisomy 18 do not survive to be born and fewer than 5 percent of babies reach their first birthdays, most with severe problems: holes in the heart, kidney defects, an esophagus unconnected to the stomach. Growth is delayed, and the child never progresses developmentally beyond six months. The head is small, with a tiny jaw and low set ears. Two telltale signs are “rocker bottom feet” and a strange overlapping of fingers in the tiny clenched fists.
But a few children with the syndrome have grown into young adulthood. Donnie’s mother Karen has devoted her life to him. Here is part of her story.
A MOTHER’S VIEW
“I was 42 when I became pregnant with Donnie. I didn’t have amniocentesis, because I don’t believe in abortion and I didn’t think there would be anything wrong. I thought he’d be a healthy bouncing baby boy, until he was born.
They called him a vegetable at birth. Donnie’s godmother is an RN and she was in the delivery room. She knew there was something wrong. The first doctor to see him knew what was wrong. He said, ‘take him home and love him and he’ll die in your arms.’ They said he’d be blind and hearing impaired, and he’s not. And he has full blown trisomy 18, he’s not a mosaic.
Donnie’s low functioning. He’s had pneumonia three times this year. He lived through a C. difficile infection. He has fevers, heart and bowel problems, and urinary tract infections, and he breaks his fragile bones. He doesn’t walk or talk. He weighs 55 pounds, and he won’t get any bigger. But he keeps on going.
He’s definitely not a vegetable. He’s a little person. He reacts appropriately. I use a suction machine and when I put the part near him, he opens his mouth. He knows. He recognizes people. His face lights up when he sees people he knows. I can’t quite comprehend that he’s that rare, but according to the geneticist, Donnie is believed to be the oldest person in the world with trisomy 18.
He loves his special needs school, and I’m heartsick because he’s aging out of everything. He loves music, and being on the school bus with other kids. I’ll have to stop calling him a kid!
He vocalizes. I know when he’s wet his diaper. He makes happy noises. We like watching game shows on TV. He likes the different colored lights, the sound of the clapping. He picks up on the excitement. He lies in a big lazy boy chair, and I sit on the couch right beside him. We like Wheel of Fortune, The Price Is Right, and Let’s Make a Deal.
There’s a light inside those eyes, I can see it. Donnie amazes me.”
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A Very Special Birthday for a Young Man with Trisomy 18 by DNA Science Blog, unless otherwise expressly stated, is licensed under a Creative Commons Attribution 3.0 Unported License.