LOS ANGELES (Reuters) - Ely Bowman, like most four-year olds, is a bundle of energy. He spends his days riding his toy car though the backyard of his Irvine, California, home, bowling with his pint-size ball and pins, and dancing under his bedroom disco ball.

But every two weeks, things are not so fun. Ely and his parents, Bekah and Danny Bowman, go to Children’s Hospital of Orange County, fighting to save his life.

Ely has CLN2, one of many types of a fatal disorder called Batten disease. His brother, Titus, died of it last year at the age of six.

The disease is extremely rare, only occurring in about two to four of every 100,000 U.S. births, according to the National Institute of Neurological Disorders and Stroke. Inherited from parents who each carry a recessive gene, it has no cure, but a breakthrough treatment is giving the Bowmans hope.

Doctors are giving Ely a drug newly approved by the U.S. Food and Drug Administration, Brineura. It acts as a replacement for an essential enzyme his body does not produce: TPP1.

“Imagine this enzyme is a little Pac-Man that’s going into the nerve cells and eating up the junk that’s building up inside neurons,” the hospital’s Dr. Raymond Wang said. “Because he can’t make it himself, he is now getting every two weeks an infusion ... into his brain.”

While not a cure, the treatment aims to delay the effects of Batten disease, which can include speech impairment, blindness, and dementia. Wang hopes in Ely’s case, the drug will be a lifeline, postponing any effects until a better treatment, or even a cure, is discovered.

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Bekah Bowman believes it is working.

“Titus at this age was growing fairly clumsy. He was falling a lot and he was having a lot of seizures. Ely, while still clumsy, he’s not falling like Titus was. And he is not having any seizures yet,” she said.

The treatment does not come cheap. Brineura can cost as much as $700,000 a year. While the Bowman’s insurance picks up the majority of the costs right now, they will have to re-appeal for approval next year. Family friends started a fundraiser, gofundme.com/team4titus, to help with expenses.

Right now, however, the Bowmans are not focusing on bills; they are savoring their moments with Ely.

“I see Ely playing ... and I just appreciate it in a whole different way,” Bowman said.