[Abaanto]

Researchers have identified a mysterious new disease that has left scores of people in Asia, notably in Thailand, and some in the United States with Aids-like symptoms even though they are not infected with HIV.

The patients’ immune systems become damaged, leaving them unable to fend off germs as healthy people do. What triggers this is not known, but the disease does not seem to be contagious.

"This is another kind of acquired immune deficiency that is not inherited and occurs in adults, but doesn’t spread the way Aids does through a virus," said Dr Sarah Browne, a scientist at the US National Institute of Allergy and Infectious Diseases.

She helped lead the study with researchers in Thailand and Taiwan where most of the cases have been found since 2004. Their report was published in the New England Journal of Medicine on Thursday.

"This is absolutely fascinating. I’ve seen probably at least three patients in the last 10 years or so" who might have had this, said Dr Dennis Maki, an infectious disease specialist at the University of Wisconsin in Madison.

It’s still possible that an infection of some sort could trigger the disease, even though the disease itself doesn’t seem to spread person-to-person, he said.

The disease develops around age 50 on average but does not run in families, which makes it unlikely that a single gene is responsible, Browne said.

Some patients have died of overwhelming infections, including some Asians now living in the US, although Browne could not estimate how many.

The virus that causes Aids – HIV – destroys T-cells, key soldiers of the immune system that fight germs. The new disease doesn’t affect those cells, but causes a different kind of damage.

Browne’s study of more than 200 people in Taiwan and Thailand found that most of those with the disease make substances called autoantibodies that block interferon-gamma, a chemical signal that helps the body clear infections.

Blocking that signal leaves people like those with Aids – vulnerable to viruses, fungal infections and parasites, but especially micobacteria, a group of germs similar to tuberculosis that can cause severe lung damage.

Researchers are calling this new disease an "adult-onset" immunodeficiency syndrome because it develops later in life and they don’t know why or how.

"Fundamentally, we do not know what’s causing them to make these antibodies," Browne said. Antibiotics aren't always effective, so doctors have tried a variety of other approaches, including a cancer drug that helps suppress production of antibodies. The disease quiets in some patients once the infections are tamed, but the faulty immune system is likely a chronic condition, researchers believe.

The fact that nearly all the patients so far have been Asian or Asian-born people living elsewhere suggests that genetic factors and something in the environment such as an infection may trigger the disease, researchers conclude.