Children's Health

Genetic Mutations Linked to Stuttering

Feb. 10, 2010 -- Researchers with the National Institutes of Health (NIH) have identified three genes that may predispose people to stuttering -- a condition that affects 3 million Americans and 5% of young children.

Because stuttering tends to run in families, it has long been suspected that genes play a role in the speech disorder.

In unique genetic research involving families with clusters of persistent stutterers, investigators with the NIH's National Institute on Deafness and Other Communication Disorders (NIDCD) identified a likely location of gene variants associated with the disorder.

In their latest research, the researchers found specific gene mutations that appear to lead to stuttering.

The findings appear today online in the New England Journal of Medicine.

Jane Fraser, president of the support and education group Stuttering Foundation of America, calls the identification of a genetic component associated with the disorder a big step forward.

"For adults who stutter this is huge because it proves there is a biological reason for stuttering," she tells WebMD. "So many people who stutter feel extreme guilt and think that if they just tried harder they could get over it."

She adds that for many parents of children who stutter, the news will come as a relief.

"Every day we get calls from parents asking what caused their child's stuttering," she says. "What they are really asking is, 'Did I cause it?' We can now say with a lot more assurance that the answer is no."

Normal speech involves a series of coordinated muscle movements associated with breathing, voice production, and movement of the throat, palate, tongue, and lips. These muscle movements are controlled by the brain and monitored through the senses of hearing and touch.

This normal speech is disrupted in stutterers, but the cause of this disruption has not been understood.

While stuttering affects all ages, it most often occurs in young children who are still learning verbal communication.

Roughly one in 20 children has the condition. Young boys are twice as likely to stutter as young girls; older boys are three to four times more likely to stutter than older girls.

Most children eventually outgrow stuttering; about 1% of adults stutter.

Identifying Genetic Mutations

In the newly published study, NIDCD geneticist Dennis Drayna, PhD, and colleagues built on earlier work involving 46 Pakistani families with large numbers of persistent stutterers.

They identified mutations in a gene known as GNPTAB in the family members who stuttered and looked for these gene mutations in 46 stutterers from the original families and 77 Pakistani stutterers that were not members of these families.

The study also included close to 550 stutterers and non-stutterers living in the United States and the U.K.

The GNPTAB mutations were present in many of the stutterers but in none of the non-stutterers.