When Derek Sedefian was barely two weeks old, his mother noticed he had trouble breathing. One day, Derek's heart failed, and though he was revived, his ailment puzzled even the most experienced doctors.

A month later, Lynda and Greg Sedefian received the diagnosis while waiting at Children's Hospital in Boston for their son's heart biopsy: Derek had Barth syndrome, a rare and often deadly disease that affects one in 500,000 boys.

"I had never heard of it," Lynda Sedefian said. "At the time, I was told it was extremely rare and that there was very little hope."

The genetic disorder affects only boys, weakening their immune systems and hearts. Most children die young if not properly diagnosed.

For seven years, the Sedefians struggled alone, dealing with their son's illness in isolation. Then one day, desperate for emotional support, Lynda Sedefian decided to try something new. She logged onto the Internet.

"I needed the support," she recalled. "It was too lonely trying to deal with this on a day-to-day basis. I couldn't do it anymore."

Sedefian found a grass-roots support group for families dealing with Barth syndrome. "It felt like I had just made a connection."

Around the world, other parents struggling to cope with their children's rare genetic diseases are using the Internet to find other families going through the same thing, to research the obscure illnesses, and even to raise money for research.

An Illinois mother launched a support group for Pierre Robin syndrome; doctors for a Pennsylvania boy encouraged his mother to use the Internet to study his rare disease; a Texas father formed an international support group that helped families trade experiences in cyberspace.

"What I love about the Internet is now families come as close to an equal partner without having gone to medical school," said Carolyn Bay, a geneticist at Children's Hospital of Pittsburgh who treated a boy with Batten disease. "Parents never stop. They keep going. They push, and they control and do everything in their power, including using the Internet."

One American in 10 is diagnosed with a rare disease, each of which affects fewer than 200,000 people, according to the National Organization for Rare Disorders (NORD). These so-called "orphan diseases" are rare ailments that have failed to attract the coveted millions of research dollars needed to find cures or treatments because they afflict few people.

Collectively, the organization says, there are more than 6,000 orphan diseases, from Adams-Oliver syndrome (malformed arms and legs) to Zellweger syndrome (high iron and copper levels in infant blood) affecting about 25 million Americans.

Before the dawn of technology, families coping with a rare genetic disease often struggled alone. There were no neighbors to turn to with the same condition. Support could be found only by long-distance phone calls or letter-writing to other families whose names were often provided by doctors.

"The Internet has changed that a lot in recent years because people are starting support groups online, and they go to each other for comfort and learn from each other's experiences," said Abbey Meyers, president of NORD, based in Fairfield, Conn.

By the late 1990s, most nonprofit foundations had Web sites where parents could ask questions and get an instant response with the click of a mouse.

"Literally, a solution is at the stroke of your fingers," says Kathy Hunter, who founded the International Rett Syndrome Association in 1984. "It's cathartic. It gives you a place with people who will listen, people to walk you through the grief process."

Still, medical experts advise caution and point to the numerous Web sites with misleading or inaccurate information that can do more harm than good for a patient's health.

"The physician-patient relationship is paramount," said Herman I. Abromowitz, a family doctor from Dayton, Ohio, and trustee of the American Medical Association. "The Internet should only complement and not replace the communication between patients and their physicians."

Since logging onto the Internet two years ago, Lynda Sedefian has been active with the Barth Syndrome Foundation, which evolved from an informal online family support network.

"We're like an extended family. We've become so close," she said, referring to the Bowens in Florida, the Wilkinses in Nebraska and the Dunns in Massachusetts.

Sedefian chats daily online with the other Barth parents, who are crusading to raise money for research they hope will eventually lead to a cure for Derek and an estimated 100 other boys.

"A lot of these kids look healthy, but you don't know that they're walking around day-to-day with a life-threatening disease," Sedefian said.

For the longest time, Susan Balog had no clue what was wrong with her son. Zachary was born healthy but soon began to have seizures. His sight, speech and motor skills deteriorated. Tests came back inconclusive, and doctors suspected a cellular disorder.

For a year and a half, the 36-year-old mother of two from Cranberry Township near Pittsburgh spent several hours a night on her computer doing homework on rare diseases. A break came when a neuro-ophthalmologist found a bulls-eye shaped dot on the retina of the 7-year-old boy's eyes.

In March 2001, Zachary was diagnosed with late infantile Batten disease, a rare genetic disorder that robs children of their mental abilities. There are about 500 cases worldwide, and children usually do not survive past age 12.

Since the diagnosis, the Balogs have sponsored charity events, raising $150,000 for the Nathan's Battle Foundation named after 8-year-old Nathan Milto, who also has the disease.

For a decade, Nancy Barry, a divorced mother from Quincy, Ill., knew of no other family struggling with Pierre Robin syndrome. Her 14-year-old son, David, was born with the disorder, a deformity that causes breathing and feeding problems that can cause children to choke.

"I was so alone when David was younger," recalled Barry, 44. "There was no Internet. I had no one to go to but the doctors, who were great, but they don't help you with the parenting aspects."

In 1998, Barry went online for the first time and typed in PRS. She found several families with special-needs children but no one with PRS. Determined to reach out to PRS families, Barry founded her own online support group -- Pierre Robin Network -- a year later.

The group now has more than 300 members from the United States, England, Australia and South Africa who communicate through e-mail messages and electronic message boards.

One thing the group doesn't do is offer medical advice.

"We try to put out a lot of tips and helpful information," Barry says. "The big thing we don't give is medical advice. We're not doctors. We're parents."

After the birth of two sons with the same rare disease that left them mentally retarded, David Hughes longed to talk to other parents.

He learned there were only about 100 boys with the X-linked Alpha Thalassemia Mental Retardation syndrome scattered around the globe with no way to communicate. Hughes taught himself computer coding for Web sites and created a site in honor of 9-year-old Barak and 7-year-old Zecharias.

In 1998, Hughes expanded his site to include support groups for other orphan diseases. The International Rare Disease Support Network has since grown to 10,000 members representing 1,200 rare diseases in 50 states and 200 foreign countries.

"I just thought it would be nice to have a single Web site dedicated to providing support groups for people affected by these little-known diseases and disorders," said Hughes, 42. Families from all over post their personal histories, offer advice and receive emotional support. The site offers links to genetic counseling, research and clinical trials and has a disclaimer warning users against taking medical advice without consulting a doctor.

In 1993, the federal Office of Rare Diseases was created within the National Institutes of Health, charged with promoting research on orphan diseases. In 2002, about 18 percent of the NIH's $23 billion budget, or $4.1 billion, was allotted to rare disease research.

In hopes of speeding up research trials for experimental drugs, many nonprofit foundations have raised their own money and appointed their own medical advisory boards of top-flight scientists who consult with the foundations about the latest research and treatments.

The Barth Syndrome Foundation set a goal to raise $750,000 over five years through donations and fundraisers. The group, which has raised $500,000 so far, will make its first grants to medical research by the end of the year, according to foundation president Shelley Bowen.

"We've moved beyond the capacity of moms supporting moms," Bowen said. "We're proactively forging roads."

Derek Sedefian, 9, greets his mom, Lynda, after getting off the school bus near their home in Voorheesville, N.Y. Derek suffers from a rare and deadly disease known as Barth Syndrome. Derek Sedefian drinks warm milk after taking the after-school medications that his dad, Greg, prepared. Derek's disease, Barth Syndrome, affects one in 500,000 boys.