A 4-year-old boy who suffered a severe case of lead poisoning after swallowing a contaminated toy that stayed in his stomach for three weeks has recovered without apparent brain damage, the Centers for Disease Control and Prevention reported yesterday.

Doctors consider the boy's case noteworthy because the lead level in his blood reached 123 micrograms per deciliter, a reading commonly associated with coma or death. The CDC's threshold of concern is 10 micrograms.

Lead is a potent neurotoxin that can permanently limit intellectual development and cause psychiatric problems and antisocial behavior. In adults, exposure is linked to high blood pressure, kidney problems, stroke and heart disease.

The boy swallowed a toy necklace pendant made in India that was about 40 percent lead. About 1.4 million were stocked in vending machines in malls, discount stores and supermarkets nationwide last year. All were recalled in September 2003 by the distributor, L.M. Becker & Co. of Kimberly, Wis., in cooperation with the Consumer Product Safety Commission.

The CDC said more pendants may still be for sale and warned doctors to consider lead poisoning in any child who puts a metal object in his mouth. The Oregon child was the only one known to be harmed, according to Becker's Web site.

The CDC's Morbidity and Mortality Weekly Report said the boy was brought to a doctor in July 2003 with cramps, vomiting and diarrhea. He improved, but the intestinal distress returned a few weeks later. This time a doctor diagnosed a virus and anemia.

Two days later he came back to the emergency room with constipation and abdominal pain that kept him from eating and sleeping. An X-ray showed the pendant, and doctors believed he would pass it. But the next day a CT scan showed it had moved in the wrong direction, and doctors decided to snatch it with an endoscope inserted down his throat. They retrieved the pendant -- and a quarter -- and sent him home. But three days later doctors tested his blood and found the worrisome blood-lead reading.

After chelation therapy the boy's blood-lead level fell below 40 micrograms. Nearly a year later, neurological, cognitive and speech evaluations all indicated that the boy is experiencing "appropriate development," the CDC said.

Bruce Lanphear, a professor at Cincinnati Children's Hospital, who has done many studies of childhood lead exposure, said it's impossible to tell whether the boy will suffer permanent deficits without knowing his IQ before he swallowed the toy.

"It could have been that he was a genius before and now he is not," Lanphear said. Scientists don't understand yet why some children are more vulnerable to lead exposure than others, and genes may have something to do with it, he said.

Zane Horowitz, an Oregon Health & Science University toxicologist who consulted on the case and helped write the CDC's report, said things could have been worse.

"My guess is he will probably be fine in the long run," Horowitz said. "He was exposed for a pretty short time. He got chelated very aggressively and early. It's long-term exposure that really is the high risk. . . . People taking lead in on a daily basis in the early years of their lives are clearly at the highest risk."