Washington ? Doctors were stumped. Tests for meningitis, cancer, a list of other diseases all were negative – yet just days after a sudden high fever sent 8-week-old Anthony James Mingione to the hospital, he died.

An autopsy uncovered the lethal secret: Anthony was born without a working immune system. A rare genetic disorder known as the “bubble boy disease” rendered him vulnerable to the most minor of germs.

Now Wisconsin is about to begin the nation’s first experiment at testing newborns for this killer, officially named SCID, in hopes of giving babies like Anthony a chance at lifesaving treatment – even as scientists ask how many infant deaths attributed to infections really might be due to the immune destroyer.

“These people look like the Gerber baby until they get sick,” said Dr. Rebecca Buckley, a SCID specialist at Duke University and longtime advocate for newborn screening.

“I am more concerned than ever that a lot of these babies never make it to the pediatrician, much less an immunologist.”

But no one knows how often SCID is missed.

“We think there’s a lot more out there and that the infants just die,” said Dr. Jack Routes, a pediatrician at Children’s Hospital of Wisconsin. He is heading the newborn-screening experiment, with funding from a parents’ advocacy group, the Jeffrey Modell Foundation, that may help answer that question.

Catching the disease before a baby gets sick means a far better chance that treatment is successful, explains Dr. Jennifer Puck of the University of California, San Francisco.

Puck developed the first screening test that promises early diagnosis. This winter, Wisconsin’s state laboratory begins the first phase of its pilot project, practicing with Puck’s test on anonymous newborn blood samples. If no problems crop up, later this year Routes and colleagues will begin a study that attempts to screen all Wisconsin newborns for SCID.

About the disease

Between 40 and 100 U.S. babies are estimated to be diagnosed each year with SCID, or “severe combined immunodeficiency disease.”

The best-known victim was Houston’s famous “bubble boy,” David Vetter, who lived in a germ-proof enclosure until his death at age 12 in 1984.

“I know this will change the course of SCID,” said Anthony’s mother, Tara Mingione of Long Island, N.Y., who has pushed for screening since his death two years ago. “Anthony had absolutely no chance to live unless he was tested at birth.”

Today, all U.S. newborns are tested for a variety of rare but devastating genetic diseases – using a single spot of blood from the baby’s heel a day after birth – to catch the few thousand who need fast treatment to avoid serious problems.

Not yet on that list: SCID and other “primary immunodeficiency” diseases, meaning children are born with faulty immune-system genes.