Over the weekend Erin Brockovich made the news yet again as she and her nonprofit team descended on the village of Le Roy, N.Y., determined to test for environmental toxins that might be giving the town's teenagers symptoms of Tourette's syndrome. She has reportedly been stonewalled thus far by local officials, who have already ruled out toxins as the cause of last October's sudden outbreak of tics and involuntary movements in 12 girls who attend Le Roy Junior–Senior High School. An environmental testing company surveyed the air and water and found nothing amiss, and a local neurologist concluded upon examining the girls that they had "conversion disorder," a catchall moniker for physical symptoms that originate in the mind because of stress, trauma or even mass hysteria.

But many of the affected kids, their parents, concerned locals and outside experts are unhappy with that diagnosis, especially as the number of teens with symptoms has risen to 15 in recent weeks. Some experts think the doctors should revisit the idea that the teenagers might have PANS—pediatric acute-onset neuropsychiatric syndrome.

PANS is a new name for an old idea: that infections by bacteria, viruses or parasites can cause the sudden onset of neuropsychiatric ailments such as Tourette's and obsessive-compulsive disorder (OCD). (Tic disorders like Tourette's are closely related to OCD, sharing many symptoms and often coexisting in patients.) PANS is more commonly known by its former name, PANDAS—pediatric autoimmune neuropsychiatric disorder associated with streptococcal infection—because the first known cases were in kids who had strep throat and then suddenly developed OCD. But researchers have realized in recent years that a variety of infectious agents—not just strep—can cause mental illness.

New Jersey–based doctor Rosario Trifiletti, who specializes in PANS, visited Le Roy, about 50 kilometers southeast of Rochester, last weekend to take blood and tissue samples from some of the afflicted girls, so he can test for such an infection. The results of those tests will be ready in a couple weeks. In the meantime, OCD expert Michael Jenike, a professor of psychiatry at Harvard Medical School, explains what PANS is and why it might account for the mysterious illness in Le Roy.

[An edited transcript of the interview follows.]

What is PANDAS, and why is it now called PANS?

It's the sudden onset of a neuropsychiatric disorder: OCD, anorexia or psychosis, cognitive problems. Initially, PANDAS was associated with strep. It turns out that other infections like mycoplasma, certain viruses, Lyme disease—these also produce the same thing. So it's not necessarily associated with strep, and they changed the name to reflect that. Now it's any sudden-onset neuropsychiatric disease.

I've even seen it in old people after they have mono, they suddenly have OCD. I've seen a lot of it after Lyme disease now, too.

How can an infection cause a mental illness?

It's an autoimmune issue. Mady Hornig at Columbia University has a mouse model that shows how it works. They give strep to mice, then give them another agent that breaks down the blood–brain barrier, and that induces a neuropsychiatric syndrome: the mice have trouble running mazes, and so on. Then they purify the antibodies from those mice, inject them in another mouse that never had strep, and that mouse gets the neuropsychiatric symptoms, too. That shows it's the antibodies doing the damage.

[For more on Hornig's studies and the mechanism behind PANS, click here.]

The neurologist treating the Le Roy teenagers ruled out PANDAS early on. As he explained to WGRZ news in Buffalo, he nixed the idea because PANDAS is exceedingly rare and it mostly strikes kids under age 11.

I used to think it was very rare, too. I've work on OCD my whole career, and I couldn't figure out why no one could pin down what was going on with these kids who had had strep. Then the parents got me involved, and I learned a lot more. I now think PANS is extremely common—way, way more common than we thought. I get e-mails from parents every day whose kids have it. I don't think it is rare, is the bottom line.

The problem is, some doctors don't know about it, and some don't even think it exists, so it isn't diagnosed.

As for the age range, I think that the figure usually used is from around two or three years old up to age 14. I don't know why things would dramatically change so that teens could not be susceptible a couple years later. You don't rule people out because of age, especially when it is just a year or two. I see mono causing OCD in people who are 70 or 80.

The neurologist also said he ruled out PANDAS because only one of the girls had a throat infection.

Unless you have a really good medical history, it's easy to miss signs of many of these infections. Parents say no, the kid hasn't been sick, but maybe there was a fever one day that nobody could explain and they forgot about it. Often these infections are very subtle. If strep is in the sinuses, for instance, a throat culture might come back negative. But if you do the blood test and get the patient's antibodies, you can often figure out if there was some sort of infection without symptoms. That's what Trifiletti will be able to do.

Some girls are reported to be getting better on their own. Is that consistent with PANS?

Yep, sometimes that happens, there's a very variable course.

What else makes you think these cases could be PANS?

I saw a couple of the Le Roy girls on TV this morning. It looked like they were displaying Sydenham's chorea, with involuntary arm and hand movements. It looks very weird to the untrained eye, like something they are doing on purpose. You can look it up on YouTube, and you'll see patients making similar movements to what these girls are exhibiting. I think that's pretty revealing. In the 1990s Susan Swedo at the National Institute of Mental Health was studying Sydenham's chorea and she made a link between it and OCD. Then she noticed a kind of sudden onset OCD that seemed to be associated with strep throat, and coined the term PANDAS.

So if does turn out to be PANS, what will the treatment be?

There are many approaches. The simplest thing is to use antibiotics. You'd probably do a three- or a six-week course. That works for a lot of kids. If it doesn't work, there are alternatives like steroids or IVIG [intravenous immunoglobulin, derived from human donor blood and used to treat autoimmune diseases].

We need more studies to figure out the best treatments. I'm starting an antibiotic study now with my [Massachusetts General Hospital] colleague Dan Geller, because there are no good studies of antibiotics for PANS.

Any final thoughts about this case in Le Roy—the fact that all these teens came down with tics at the same time?

It's very weird. Usually I don't think you get outbreaks very often of things like PANS, where you have a whole group of kids get it. However, if there is strep or something going around a school, it's possible that this might happen more than you think. Some kids might stay home from school from awhile, maybe see psychiatrists in private—it's under the table, it doesn't get out there and people don't put it all together.

I just can't imagine that it's conversion or mass hysteria; that diagnosis doesn't mean much. It's a name people stick on things when they don't understand what's going on. Some psychiatrists like these names, thinking if you give something a name it sometimes helps people, but I find it just confuses the issue.

This case really forces the issue. Whether it's the toxins or PANDAS or whatever, I think we will learn a lot from it.