Finding out your child has a rare disease can be especially difficult because of limited research and treatment options.
Although 12-year-old Hunter Propst had some behavior problems, he grew up fairly similar to other children. Doctors diagnosed him with ADHD and autism.
"We always wondered what was going on with Hunter because he never quite fit them, and he was never getting better and was never doing the things the other kids would do," Hunter's mother, Darci Bible, said.
In fact, over the last couple years Hunter's condition got much worse.
"Hunter isn't able to carry on a conversation with anyone as far as if you were to ask him a question," Bible said.
After dozens of tests, doctors diagnosed Hunter with a very rare disease called Sanfilippo syndrome. It's a metabolism disorder passed down through families.
"Children with Sanfilippo syndrome sometimes live to their twenties, but mostly they live into their teens," Bible said.
Currently there is no cure and little treatment for the disease.
"You see them progressing, and you can't help them. He can't tell me if he doesn't feel good or if he has a tummy ache or earache," Bible said.
Hunter now struggles to walk and talk.
"They say he functions on about a cognitive level of about a 17 month old child," Bible said.
Still, the family is trying to look at the positive and enjoy every minute with Hunter.
"You just can't help but fall in love with him. He loves life. He's happy, which is a good thing. He doesn't know he's any different than anybody else, and I think that's the most important part. He's happy," Bible said.
For more information, check out http://www.rarediseaseday.org/