An estimated 20 million people in the United States suffer from peripheral neuropathy, marked by the degeneration of nerves and in some cases severe pain. There is no good treatment for the disorder and in one third of the cases, doctors have not been able to find an apparent cause.
Now, a new study, published online June 22 in the Annals of Neurology, has found that mutations of a single gene are linked to 30 percent of unexplained neuropathy cases. These findings could lead to desperately needed pain treatments for victims of this debilitating disorder.
The study was conducted by an international team of scientists headed by researchers from Yale University, the Veterans Affairs Medical Center in West Haven and the University Maastricht in the Netherlands.
"For millions of people, the origin of this intense pain has been a frustrating mystery," said Stephen Waxman, MD, Yale neurologist and a co-author of the study. "All of us were surprised to find that these mutations occur in so many patients with neuropathy with unknown cause."
Study Design and Results
The study focused upon mutations of a single gene — SCNA9 — which is expressed in sensory nerve fibers.
- Waxman's group had discovered that mutations in this gene's product — the protein sodium channel Nav1.7 — cause a rare disorder called "Man on Fire Syndrome," characterized by excruciating and unrelenting pain.
- Colleagues in the Netherlands carefully scrutinized neuropathy patients to rule out all known causes of the neuropathy, such as diabetes, alcoholism, metabolic disorders and exposure to toxins.
- Researchers then did a genetic analysis of 28 patients with neuropathy that had no known cause. They found 30 percent of these subjects had mutations in the SCN9A gene.
- They also discovered that the mutations cause nerve cells to become hyperactive, a change they believe eventually leads to degeneration of nerve fibers.
"These findings will help us as clinicians to a better understanding of our patients with small fiber neuropathy and could ideally have implications for the development of future specific therapies," said University Maastrict co-author Catharina G. Faber, MD, PhD.
I find this ever-expanding field of genetic testing to be exciting and encouraging. Just think about it. Millions of people who have suffered for years without knowing the cause of their painful neuropathy, may now at least get an answer to what is causing their pain. (As a fibromyalgia patient who suffered for seven years before being diagnosed, I can tell you what a tremendous relief it is to at least know what is causing your pain.)
Of course, the next big step for scientists is to build upon this new-found knowledge and develop effective treatments to relieve the pain.
I can't help but wonder how many other cases of unexplained chronic pain will finally be identified as the field of genetic testing continues to grow. It gives me great hope. Every person who lives in chronic pain deserves to know the cause of their pain.
Faber CG, et al. “Gain of function Na(V) 1.7 mutations in idiopathic small fiber neuropathy.” Ann Neurol. 2011 June 22. [Epub ahead of print]
“Yale Researchers Uncover Source of Mystery Pain.” Yale Univeristy News Release. June 22, 2011.
Published On: June 30, 2011