A federal health agency on Wednesday launched a study into an unexplained skin disorder that causes a crawling sensation and lesions that won't heal, the first attempt to determine whether Morgellons is a legitimate illness or caused by the patient's imagination.

Dr. Michele Pearson, principal investigator for the Centers for Disease Control and Prevention, would not go so far as to acknowledge that the illness is real, but said the agency has received enough inquiries about it during the past year that it deserves to be considered, and hopefully explained.

"I'm not so concerned with the label," Pearson said. "Clearly the suffering that these patients are experiencing is real."

Many families in Houston are self-diagnosed with the condition, making the area a Morgellons hot spot, according to the Morgellons Research Foundation, a nonprofit group that has become the primary source of information about the disorder.

People who report suffering from the condition identify a range of symptoms including crawling, biting and stinging sensations and so-called fibers or black specks that protrude from skin lesions. Some also suffer from fatigue, mental confusion and joint pain.

But there's skepticism in the medical community about whether the illness actually exists. Many doctors believe patients that show those symptoms suffer from delusional parasitosis, a psychotic illness that causes the patient to believe they are infected with parasites.

More than 11,000 families have contacted the foundation indicating they believe they have the illness. About 800 of those are from Texas, with most clustered around Houston, San Antonio and Dallas.

"What needs to be done ultimately and quickly is that the cause of this illness needs to be identified," said Mary Leitao, a biologist who gave the disorder its name and founded the foundation in 2002 after her 2-year-old son began showing symptoms. "It's frustrating to have a sick child and not be able to get help, to have to find your own answers, fight through a system, and then to be treated in such a cruel way by certain groups that just cannot accept that this is real."

The agency's study, in conjunction with Kaiser Permanente, a health care group in northern California, is intended to gather information about the illness, including common symptoms, possible causes and risk factors shared by people who say they suffer from it. Researchers will look only at patients in northern California, the state with the highest number of self-reported cases.

So little is known about the illness that the Houston Chronicle could not locate a local doctor who could talk knowledgeably about it.

Pearson said there's no evidence that Morgellons (pronounced mor-GELL-uns) is contagious, but patients frequently report their family members also show symptoms.

The illness has turned Waco resident Pam Stelk's life upside down. She began to show symptoms about a year ago, and since then has had to quit her job and move away from her family because of the painful bites on her skin and other symptoms.

"To me it's just the most terrible thing that I can think of that I could have," said Stelk, a 53-year-old who worked as a drug counselor. "You just hate the thought of them things munching on you."

When she picks the black specks - which she believes are living - out of her skin lesions, the stinging sensation subsides, she said. But doctor after doctor will not believe her story. They tell her she's crazy, she said, fighting back tears.

"It's bad enough that you have it," she said. "It's even worse that the medical community does not know or will not acknowledge that it's a possibility."