Stanford University researchers have determined that the sleep disorder narcolepsy is an autoimmune disease. The finding, published in the May 3 online issue of Nature Genetics, links narcolepsy to mutations of two genes involved in critical roles in protecting the body from disease. These two variations, the researchers say, are likely conspirators against hypocretin, a wakefulness-promoting hormone that narcoleptics have been found to lack.

     "This is a very important finding," commented sleep disorder expert Merrill Mitler, program director at the NIH National Institute of Neurologic Disorders and Stroke. "It puts in place another piece of the puzzle and shows a way to link [this gene variant] to hypocretin-containing neurons via an autoimmune attack."

     Narcolepsy, a condition which affects one in 2,000 people, is characterized by daytime drowsiness, including brief but sudden bursts of sleep during the day, irregular sleep at night, and cataplexy, a sudden loss of muscle tone and strength.

     The researchers conducted genetic studies on 1,800 people with a variant for the human leukocyte antigen, or HLA, gene, which helps the immune system identify foreign bodies it needs to eliminate to protect the body. Previous studies had linked the HLA variant to narcolepsy, a condition that nearly half the study subjects had. The Stanford team found that all the study participants with narcolepsy also had a mutated gene link to T-cells, which are vital cogs in all the body's immune responses.

     Dr. Emmanuel Mignot, a professor of psychiatry and behavioral science and Director, Stanford University Center for Narcolepsy, said it's likely that HLA and the T-cell variant interact in a way that kills hypocretin cells although his team's findings did not determine that direct relationship.

     If further studies can reveal that the two mutations work together, scientists may be able to identify people predisposed to narcolepsy and find ways to prevent its development, according to Dr. Mignot. It may also lead to discoveries concerning other more common autoimmune afflictions, such as multiple sclerosis and juvenile diabetes.

     Dr. Mignot commented, "For a long time, people have suspected narcolepsy had something to do with the immune system--that it was killing cells that produce hypocretin. But there hasn't been direct proof. Our discovery clearly shows narcolepsy is an autoimmune disease."

--Source: Adapted from "Research IDs Narcolepsy as Autoimmune Disease," Kevin McKeever, 2009 HealthDayNews, Inc., May 4, 2009; and "Narcolepsy is an Autoimmune Disorder, Stanford Researcher Says," Stanford University School of Medicine, contact Michelle Brandt, May 3, 2009