A potentially fatal but treatable immune disorder known as "bubble boy" disease is rare but twice as common as previously believed, according to a UCSF-led study published Tuesday.

Researchers, in what's considered the first look at the national impact of the disease, found that severe combined immunodeficiency, called SCID, affects 1 in 58,000 newborns instead of 1 in 100,000 as previously estimated on much more limited data.

The discovery that SCID is more prevalent than believed highlights the importance of screening newborns for conditions that can be treated.

"The whole point of newborn screening is that you have to be able to do something about it, and it's really important that this is treated early," said Dr. Jennifer Puck, a pediatric immunologist at UCSF Benioff Children's Hospital San Francisco and senior author of the study, which was published online in the Journal of the American Medical Association.

She said the reason her team of researchers could collect accurate data was that several states have been screening for the disorder for the past several years. Before there was screening, Puck said, babies died after contracting illnesses because their immune systems couldn't fight back. It was difficult to know that babies had SCID until they got sick.

Severe combined immunodeficiency is caused by defects in certain genes critical for fighting infections. Newborns can be cured if tests catch it early enough - before an illness sets in.

In 2010, the federal government recommended screening infants for SCID for that reason. The most common treatment for the disease is a bone marrow transplant, and it has been highly successful. But screening is essential, researchers say.

TV movie based on real case

The disease became known to the public as "bubble boy" disease because of the 1976 John Travolta TV film "The Boy in the Plastic Bubble." The film was inspired in part by the most famous SCID patient, David Vetter, who lived in a sterilized chamber his entire life until his death from complications in 1984 at age 12.

"Back in those days there were not good treatments for infants born with (SCID)," said Puck, who has been studying the disease for more than two decades. "The original boy in a bubble had to be put in a germ-free environment to protect him. A cold or a virus that would put a healthy person back for a day or two could be fatal."

Because babies are protected by their mother's immune system during the first few months of life, those born with the disease often show no sign of it until it's too late.

SCID often runs in families, but is rare enough that many generations can pass before a baby inherits it. That's why a screening test, which was developed by Puck in 2006, is critical to detecting and treating the disorder.

Although the federal government can make screening recommendations, each state determines which conditions will be included. California became the third state to add SCID to its screening program in August 2010, and now 23 states, with nearly two-thirds of all infants born in the U.S., conduct the test. Puck said some states have been slow to add new conditions, such as SCID, because of the added costs.

Saving her son's life

Jennifer Taylor of Brentwood said early screening saved the life of her son, Skyelar, who will turn 2 in October.

Just days after bringing her seemingly healthy baby home, Skyelar developed a severe rash that Taylor assumed was a bad case of cradle cap. But then she received a call from a doctor with the state health department informing her that her son may have SCID.

"I knew about the boy in the plastic bubble. I was thinking, oh my God, my baby is going to be this child that won't be able to go out in society," Taylor said.

Before even completing the tests to confirm the diagnosis, Skyelar developed a respiratory infection and was rushed to UCSF. He was diagnosed with a severe form of SCID, underwent chemotherapy to knock out any traces of an immune system, and eventually received a transplant of blood-forming cells from the bone marrow of a young man in Germany, whose specimen was flown to UCSF overnight.

After spending more than six months in the hospital, Skyelar came home on May 5, 2013. Taylor said her son is healthy, but she limits his contact with other children and public playground equipment because his condition delayed his vaccinations.

"If I would have had a child before the newborn screening test, the child probably wouldn't have made it," Taylor said. "It's very important the state does these tests because it saves little babies' lives."

Transplants like the one Skyelar received have a high success rate, even without a perfect match, because babies born with the condition generally lack the ability to reject the new cells, Puck said.

After the procedure, the babies must take human antibodies for a while. Other treatment options, such as enzyme and gene therapies, are also being explored, she said.

52 cases in California

In the study, researchers found 52 cases out of the more than 3 million infants screened in California and nine other states, plus the Navajo Nation. The disease is about 10 times more common in Navajo and Apache tribe members than the general population, Puck said.

Of the 52 cases identified in the study, three infants died before receiving treatment, four died after receiving transplants and the remaining 45 infants survived.

"If you don't find them, you can't treat them," Puck said. "If you do find them, you give them a transplant and make them into a healthy taxpayer."
