Pulmonary arterial hypertension is high blood pressure in the lungs and can be deadly without treatment. While commonly found in young adult women, one in a million children have this disease, including 11-year-old Iain Hess.

"I can't go up into the mountains because there's not enough oxygen and my lungs just can't handle it," said Iain.

Iain was diagnosed with pulmonary arterial hypertension when he was 5 years old. He has no family history of the disease.

"John and myself are really healthy people so when this diagnosis came about we were shocked," said Seema Hess, Iain's mother.

Pulmonary arterial hypertension can be hard to diagnose. The symptoms include shortness of breath, not being able to exercise, and even passing out, which are common in other disorders.

"It's related to scarring and thickening of the blood vessels in the lungs that leads to increase in pressure. Then the right side of the heart fails because it can't maintain the flow to the lungs," said Dr. Dunbar Ivy, pediatric cardiologist at Children's Hospital.

Ivy said there's no cure for pulmonary arterial hypertension at this point. So right now, Iain has to wear a pump that releases medicine to his heart.

"I can't get this pump wet. I can still swim, but have to swim with a dry suit on," said Iain.

Iain also had to give up some of his favorite sports including skiing. He can still rock climb and play baseball, but still can't overdo it.

"When we go hiking, I have shortness of breath a lot. We need to take a lot of breaks to get up to the top of the mountain," said Iain.

Our main hope is that there is something that comes up in the next 5 to 10 years that can cure this disease," said Hess.

The Hess family plans to take part in the second annual Colorado Pulmonary Hypertension Association 5K run at the University of Colorado Anschutz Medical Campus in Aurora on Sunday, Sep. 18. The Children's Hospital will also help host this event. For more information, go to FirstGiving.com.