At the age of 4, Abby was diagnosed with 22q11.2 deletion, also known as DiGeorge syndrome/IVFS. Dempster and his wife, Jenny, have stepped up to raise awareness of the disorder and help families deal with it. They know firsthand about the struggles associated with 22q11.2 because their daughter, Riley, has it.
DiGeorge is caused by deletions within the 22q11.2 chromosome. There are many different variations of the disorder, but it has interfered with Riley's ability to eat and swallow.
Born on April 1, 2009, Riley became a regular at Children's Memorial Hospital in her first six months. She needed surgery to put in a tracheostomy tube and a gastric tube for feeding as well as a procedure called a Nissen fundoplication, which reduces the reflux into her esophagus. Try explaining that to a 6-month-old kid.
Jenny Dempster went to the Internet for information, which is how she met Abby's mom, Eliza Oates, on a website for parents dealing with 22q11.2. Abby celebrated her seventh birthday on Dec. 15. She has a rare congenital heart defect and functions now with one lung, a paralyzed diaphragm and slightly low immune function. She's had two open heart surgeries.
But if you saw her at school or playing with Dempster's 4-year-old son, Brady, you'd think everything was normal.
"She's kind of a success story for us," Eliza Oates said of her daughter. "She was always sick as a baby -- lots of trips to the doctor, ear infection, sinus infection, those things. Finally at age 4, we got the diagnosis. We've teamed up with Ryan and Jenny, and I help out whenever I can. We're so thankful for them."
In its first year, the Dempsters' foundation raised more than $450,000 through its fundraisers and granted $185,600 to charitable organizations working with families of children with 22q as well as to local Chicagoland charities.
The list of events included the first Casino Night and Concert held in July at the House of Blues in Chicago. In August, about 200 people attended a fundraiser at Joe's Seafood, Prime Steak and Stone Crab in Chicago. Also in August, more than 200 people took part in the "Slow and Steady 22q Walk" in Glen Ellyn, Ill.
The Candyality candy-maker has donated $1 per pound of its Cubbie Gummie Bears to the Foundation. The Loyola men's basketball team joined the fight, and on Dec. 11, $1 from the sale of each ticket for the Ramblers' game against Kansas State plus sales from a raffle were donated to the foundation.
The Cubs players rallied around Dempster to create a cookbook with their favorite recipes. The book is available on Cubs.com, and proceeds go to Dempster's foundation. Dempster said a woman at a nearby sushi restaurant recently asked for 50 copies to give as holiday gifts.
D'Agostino's Pizza and Pub, located near Wrigley Field on Addison Street, donates $1 to the foundation for every pizza purchased on the 22nd of each month. The restaurant has hosted two fundraisers for the Dempsters' foundation, including one Dec. 10 that was attended by Ted Lilly and Kerry Wood. Ryan Dempster likes to order D'Agostino's chicken parmesan on the nights before he pitches for the Cubs.
It's that kind of grassroots effort that has contributed to the foundation's cause.
"It's been more than I ever expected," Dempster said of the response he's gotten. "Aside from all the money we've raised, just the awareness [has improved]. There's hospitals testing for it now because of our story coming out and I think that's an amazing thing. That says a lot about the parents who came before us because where would we be without them? The response has been overwhelming."
At 18 months, Riley was taking eight to 10 steps without any help. She's come a long way since those first six months when she spent almost all of her time at the hospital.
"I think one of the biggest things that you have to come to realize with these kids is that it's a syndrome," Dempster said. "Just because she gets through something doesn't mean she's not going to have something else. There are going to be things we have to be careful with. She's always going to have some immune problems where it's tougher for her to fight off a cold than somebody else. As a whole, she's doing great, she's doing really well."
So is Jenny, who is pregnant with the couple's third child, due in January. The Dempsters will have plenty of family over for the holidays. Riley is a little more aware of all of the festivities going on.
"She finds all this Christmas stuff pretty interesting," Dempster said. "Brady's at the age where he thinks in a few nights, he's going to go to sleep and then Santa is coming, so that's really cool."
Dempster, 33, remembers being Brady's age and all of the excitement that Christmas brings.
"As you become parents, you get to live being a kid all over again," he said. "That's what it is because you see yourself going through the same stages and that's a lot of fun."
Eliza Oates and her husband, John, were Cubs fans before meeting Dempster. Because of the pitcher's efforts, they're now more than fans. They're friends but also teammates as they battle 22q.
"The fact that [the Dempsters] have opened themselves up and supported other families like us and allowed us to become friends with them is really special," Eliza said.
Abby was diagnosed shortly after Christmas in 2007.
"It wasn't a great holiday but at least we had an answer because four years of struggling and not knowing what was wrong was getting to be worse," Eliza said. "We got an answer, put a team of doctors in place, moved forward and went from there.
"We have a fabulous pediatrician but pediatricians don't know [about 22q]," she said. "The key is to get doctors to recognize a host of symptoms and hopefully then get earlier diagnosis for kids missed early on."
That's the Dempsters' goal. If you get a moment this holiday, say thanks to people like Ryan and Jenny, who are giving back so families like the Oateses don't have to struggle as much with confusing medical diagnoses as they did with Abby.
"They've been pretty great for us," Eliza Oates said. "Ryan's got a heart of gold."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat This story was not subject to the approval of Major League Baseball or its clubs.