The medical condition that causes people to become excessively sleepy and even lapse into sleep involuntarily could be linked to a hereditary deficiency. The new evidence suggests that Narcolepsy is, in fact, an autoimmune disease associated with particular inherited variations in a gene that encodes a protein found on a type of immune cell. This cell type called a T cell plays a crucial role in targeting immune responses.
The genetic variation is fairly common, while Narcolepsy is rare. Among more than 2,500 participants, researchers found that people with the variation are 251 times more likely to have Narcolepsy with cataplexy, muscle weakness brought on by actions such as laughter, than those without the variation.
For the study, which was published in the journal Sleep, researchers analyzed the genetic makeup of nearly 1,300 people in Europe who suffer from Narcolepsy with cataplexy and more than 1,400 people who don’t. Nearly everyone with the condition had the genetic variation, which is linked to the functioning of the immune system.
According to the American Academy of Sleep Medicine, previous research has suggested a link between Narcolepsy and problems such as infections. One theory is that in people who are genetically susceptible
to Narcolepsy, the immune system goes out of whack and accidentally destroys brain cells that are crucial to keeping the body alert.
The authors also suggested that high-resolution genotyping, a process in which an individual’s DNA is examined, might aid in diagnosing patients suspected of having narcolepsy.
According to a University of California San Francisco study, researchers initially studied more than 1,800 Caucasians. All had the previously identified HLA gene variant. More than 800 had Narcolepsy, but the rest did not.
The researchers identified a nearly twofold elevated risk for narcolepsy associated with variations in a gene that encodes a protein called T-cell receptor alpha. They confirmed their initial findings in additional studies of Caucasians, Asians and African Americans. Researchers had previously suspected a role for T-cell receptor variants in autoimmune diseases and had searched for associations, but this is the first time one has emerged from such a study.
“This is a disease that nobody suspected was autoimmune until a very strong association with HLA was identified,” Risch says. “That was shocking — as is this new finding.”
Find out more information on Narcolepsy here, on BlackDoctor.org.
SOURCE: American Academy of Sleep Medicine, news release, Jan. 2, 2014; University of California San Francisco, news release, May 18, 2009
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