Is there a part of you that you hate to look at and perhaps try to hide from others? Do you glance at your image in distress whenever you pass a reflective surface?

Many of us are embarrassed by or dissatisfied with some body part or other. I recall that from about age 11 through my early teens I sat in class with my hand over what I thought was an ugly bump on my nose. And I know a young woman of normal weight who refuses to sit down in a subway car because she thinks it makes her thighs look huge.

But what if such self-consciousness about a perceived facial or body defect becomes all consuming, an obsession or paranoia that keeps the person from focusing on school or work, pursuing normal social activities, even leaving the house to shop or see a doctor? What if it leads to attempted suicide?

Such are the challenges facing tens of thousands of Americans who suffer from body dysmorphic disorder, or B.D.D., a syndrome known for more than a century but recognized only recently by the official psychiatric diagnostic manual. Even more recently, effective treatments have been developed for the disorder, and its emotional and neurological underpinnings have begun to yield to research.