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Questions and Answers about NIDCD Stuttering Research

June 7, 2010

From an interview with Dennis Drayna Ph.D., Chief, Section on Systems Biology of Communication Disorders, Laboratory of Communication Disorders.

Published in the New England Journal of Medicine.*

A study led by NIDCD researchers has identified three genes as a source of stuttering in volunteers from Pakistan, the U.S., and England. Read the press release here.

Q. Why are these findings important?

A. People have recognized stuttering as a speech disorder for thousands of years, and people have speculated on the causes of disorder for centuries. Now for the first time, we know at least some of the underlying causes of stuttering.

Q. You’ve found mutations in genes that are involved in cell metabolism. What does this tell us about the causes of stuttering?

A. The genes we’ve identified are associated with a metabolic function that occurs in every cell in our body. We speculate that there is a group of cells in the brain that are dedicated solely to speech production and are uniquely sensitive to the metabolic defect caused by these mutations. Identifying these brain cells and their function could provide new insights into both stuttering and normal speech.

Q. Do your findings generate new avenues for treatment of stuttering?

A. Our findings point to some potentially exciting possibilities in the future. Our findings indicate that these cases of stuttering are related to a class of well-known inherited medical disorders called lysosomal storage diseases. Over the past 10 years, a new treatment known as enzyme replacement therapy has been shown to be effective for a number of lysosomal storage disorders. There are still a number of hurdles that must be overcome, but it’s possible to imagine that enzyme replacement therapy could be used to treat these cases of stuttering someday.

Q. Your findings potentially explain only a small fraction of stuttering. What about all the other causes of stuttering?

A. Given our complete lack of understanding of the underlying causes of stuttering, our initial goal was to identify at least one cause of this disorder. We’ve now identified 3 different genes involved, and these findings have led us in a completely unexpected direction. An inherited metabolic disorder had never previously been proposed as a cause of stuttering, and we now have a number of new avenues of research open to us. In addition, other studies we are working on have revealed clear evidence for additional genes that cause stuttering, distinct from the three genes found so far. We believe we have a good chance of finding these additional genes, which will identify additional causes of stuttering.

Q. What do your findings mean today for people who stutter?

A. Our findings clearly demonstrate that stuttering is a biological disorder. They take us farther away from the view that stuttering is caused by interactions with other people, or that it is a social disorder or an emotional disorder. Our findings will hopefully help remove the stigma that has been associated with stuttering due to the misperception that stuttering represents nervousness or some sort of character weakness.

Q: Is it possible to participate in your clinical trial if I do not live close to the NIH campus?

A: Our researchers have assembled mailing kits that interested volunteers can take to their doctor and have their blood drawn. The sample and information can then be mailed back to the researchers. For more information about this clinical trial, see Protocol NCT00001604 on, or contact the NIH Clinical Center Patient Recruitment and Public Liaison Office, (800) 411-1222,

* N Engl J Med. 2010 Feb 25;362(8):677-85. Epub 2010 Feb 10.
Kang C, Riazuddin S, Mundorff J, Krasnewich D, Friedman P, Mullikin JC, Drayna D.

Prepared by: Dennis Drayna, Ph.D., Chief
Section on Systems Biology of Communication Disorders
NIDCD Laboratory of Molecular Genetics

February 22, 2010

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Last Updated Date: 
June 7, 2010