What is Trisomy 18? Rick Santorum's Daughter Has Devastating Disorder

In GOP ads and on the campaign trail, Republican presidential primary candidate Rick Santorum defended his campaign saying that his daughter Isabella, who has Trisomy 18, inspired him to keep going.

But what, exactly, is Trisomy 18, and how does it affect his 3-year-old daughter?

Santorum spoke about Bella at the Iowa Republican debate on Nov. 18. Bella Santorum has a genetic disorder, also known as Edwards syndrome, that kills roughly 90 percent of the children affected by it before during birth.

'It's always been measured in days and weeks.'

Since his revelation at the start of the presidential primary race, where he spoke of his love and commitment to his daughter, some Americans have wondered whether Rick Santorum should stay in the race. Santorum, however, defended his decision to stay on the campaign trail.

I don't know whether her life is going to be measured, it's always been measured, in days and weeks, Rick Santorum said at the annual Defenders of Freedom event in November. Yet here I am... because I feel like I wouldn't be a good dad if I wasn't out here fighting for a country that would see the dignity in her and every other child.

Many listening to Rick Santorum talk about Bella, however, have another question on their minds, especially since the GOP presidential hopeful has made treating her disorder one of the platforms of his campaign: what, exactly, is Trisomy 18?

Trisomy 18: The Basics

Trisomy 18 affects an estimated one in every 3,000 to 6,000 live births that affects three times as many girls as boys and which has devastating effects on most children.

Instead of having the normal two pairs of chromosome 18, children with Trisomy 18 have three copies, similar to the three copies of chromosome 21 found in people with Down syndrome. The extra material interferes with normal pre-natal development.

Almost all children with Trisomy 18 die before they're born, with many more dying in their first months. Only one in 10, on average, make it to their first birthday, and only 1 percent live to be 10 years old, already making Bella, whom the family calls Boo, something of an outlier.

Symptoms of Trisomy 18, which is similar to Down syndrome, almost always include mental deficiency and other developmental problems that reduce life expectancy and comfort. According to the U.S. National Library of Medicine, physical manifestations include:

• Low birth weight, a small head and jaw
• Clenched hands, crossed legs (preferred position by baby) and rocker-bottom feet (overly rounded soles)
• Undeveloped physical body (shorter fingernails, undescended testicles, low-set ears)
• Unusual, bowed-out chest shape sometimes called pigeon chest (pectus carinatum) causing breathing problems and possibly stunted heart and lung development

Tests of the infant may also reveal congenital heart disease or an array of kidney problems from stunted pre-natal development.

Prevention and Treatment of Trisomy 18

Prevention can only be achieved by genetic testing during the early stages of pregnancy, with parents terminating a trisomy 18-positive child. Examination of the pregnant mother might show an unusually large uterus and amniotic fluid.

Treatment for Trisomy 18 is incredibly varied, and is usually done on a case-by-case basis. Sepsis (when the bloodstream is overwhelmed by bacteria) is a common occurrence in children with Trisomy 18 and cardiac lesions are also frequent.

One of the best ways to improve the survival rate of children with Trisomy 18 is neonatal intensive care, though specific management of the disorder and the treatment's efficacy is still considered controversial due to the disorder's variety of symptoms and manifestations.

'We're the disabled ones.'

Rick Santorum has seven children, but in an October campaign ad, Family, he focuses on Bella, his youngest, and on the diagnosis that rocked his family.

We were told by the medical community: Why do anything? Santorum says in the ad, noting the difficulty involved in treating Trisomy 18 disorder. Santorum was angered by the idea that Bella should be allowed to die.

We understand that her life is going to be different than our other children, Santorum said. But we felt that we owed her the opportunity, the chance to do as well as she could.

The GOP primary candidate also had a unique take on his daughter's diagnosis, viewing her Trisomy 18 almost as a blessing and rejecting the idea that she is disabled.

I look at her, and I look at the joy, and the simplicity, and the love that she emits, and it's clear to me that we're the disabled ones, not her, Santorum says in the campaign ad. She's got it right.