Friday, May 8, 2009

New Study Suggests that Narcolepsy is an Autoimmune Disorder

Scientists have made another major breakthrough in understanding the sleep disorder narcolepsy. A new study suggests that it is an autoimmune disorder.

Results show that people with narcolepsy are more likely to have a unique variant of a specific gene belonging to T cells. These cells play an important role in the response of the immune system.

“Our discovery clearly shows narcolepsy is an autoimmune disease,” study author Dr. Emmanuel Mignot said in a
Stanford statement. “We’re now getting the main pieces of what’s happening in narcolepsy.”

NIH reports that one of those pieces involves a human leukocyte antigen (HLA) gene. People with narcolepsy are likely to have a variant of an HLA gene. Along with T cells, HLA proteins help the immune system identify invaders such as bacteria and viruses.

Another piece of the puzzle was
the discovery that people with narcolepsy lack brain cells that make hypocretin. This is a hormone that helps promote wakefulness. The finding helped explain why people with narcolepsy have episodes of uncontrollable sleepiness.

But the loss of hypocretin-producing brain cells occurs over time; narcolepsy typically appears after 15 years of age.

Why do these brain cells die in people with narcolepsy? The new study suggests that the immune system attacks and destroys the brain cells by mistake.

So is the case closed? Not yet. The HLA and T-cell variants fail to fully explain narcolepsy. Some people with these genetic variations never develop the disorder.

Why? That is still unclear. But Dr. Mignot believes that a chain reaction is involved.

"Narcolepsy is probably the result of a series of unfortunate events,” he told
BBC News.

Mignot said that the genetic variations “predispose” you to have narcolepsy; they put you at risk. But it may take some kind of “trigger” - such as in infection - to set the disorder in motion. This trigger may activate the immune system response that kills hypocretin cells.

There is still more to learn about narcolepsy. But this new discovery may help doctors learn how to stop the disorder from developing.

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