Kaelyn and Roman Sanabria are happy and pain free--their mom Kim said it's a far cry from not too long ago.

"Kaelyn had a lot of chest syndrome, pain crisis in her knees, swelling of the hands and swelling on the feet," Kim said. And for Roman--walking was a pain.

"With Roman," Kim said. "He had a lot of back pain crisis which when he first started walking he would just hold his back constantly, he would hold his back from being in pain."

All 50 states now have mandatory screening for sickle cell at birth--both Kaelyn and Roman were diagnosed immediately.

Sickle cell is a genetic disorder that changes blood cells to the shape of a half moon which prevents the flow of blood.

Dr. Zora Rogers is the director of hematology at Children's Medical Center and professor of pediatrics at UT Southwestern Medical Center in Dallas.

She said the results can be devastating.

"If it blocks a blood vessel to the brain you get a stroke," Dr. Rogers said. "One in ten with sickle cell anemia stroke in childhood."

Dr. Rogers added that more than 90% of kids will have kidney and spleen problems before the age of five.

Dr. Rogers and nine other doctors recently studied the impact of the cancer drug hydroxyurea on children.

The drug had reduced the number of adult complications by 50% and was used only in severe childhood cases.

Dr. Rogers found it could be used routinely on children as young as 9 months old and now offers it to all parents who have kids with sickle cell.

"Instead of just waiting for things to happen and reacting to those problems," Dr. Rogers said. "All of the sudden you have the choice to say, I will take this medicine everyday to decrease the chance that something bad happens."

The drug tricks the body into making fetal hemoglobin which doesn't form a sickle and allows the blood to flow smoothly. Kaelyn took part in the study and started receiving the drug when the study ended. So did Roman.

Today she and her brother are laughing and playing--pain free.

"He holds balls and trucks and cars," Kim said. "He's running around the house instead of holding his back all the time from being in pain."

Just like little boys should.

"I'm so grateful," Kim said.