Emily Joost, 8, can’t talk back to her parents when they talk to her, but she can smile, and that is enough for Elaine and Lyndon Joost.

Emily has Aicardi syndrome, a genetic disorder so rare that only 500 people worldwide have been diagnosed with it, the Belleville News-Democrat in Illinois reports.

She also is unable to walk or feed herself, but still the Joosts are not complaining. They said their daughter is happy, and that is all that matters to them.

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"It was very difficult for me, especially that first year," Elaine Joost said of her daughter’s diagnosis at 3 months old. "In the beginning, it was always, 'Am I going to be strong enough? Can I do this?'"

Emily can make noises to indicate if she is happy or upset, according to the newspaper, but she cannot form words.

"She smiles a lot; she’s happy," Lyndon Joost said. "And, when she starts giggling, you can’t help but laugh with her. She has this happiness around her that you can’t help but get caught up in."

Aicardi syndrome typically affects females. It is marked by the absence of the corpus callosum, a collection of nerves sitting between the right and left sides of the brain that allow the two sides to communicate with one another, according to the newspaper.

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There is no cure.

Emily has about four seizures a day, which is typical for Aicardi patients; however, her parents describe the seizures as "spasms" that usually last about 45 minutes.

Eight years ago approximately 30 percent of girls with Aicardi syndrome died before their third birthday. Now, many are living into their teen years; some even into adulthood.

Click here to read the full story from the Belleville News-Democrat and to see a picture of Emily.