Stuttering Genes' Discovery Could Lead to New Treatment

(Feb. 11) -- Scientists have long suspected that stuttering is an inherited condition, and now a research team has found three genes implicated in the common condition.

The study, led by doctors at the National Institute on Deafness and other Communication Disorders (NIDCD) has discovered that the same three genes are tied to stuttering among patients in Pakistan, the U.S. and England.

Two of the genes had already been connected to two rare metabolic disorders, mucolipidosis I and II, which inhibit a cell's ability to be broken down and recycled. Those disorders are recessive, so a person would need two copies of the mutated gene to develop them. Stutterers have one.

Until now, stuttering was largely a mystery. The speech disorder affects about 3 million Americans, and can have serious implications for one's social life, career and self-esteem. About three-quarters of afflicted kids grow out of it, but adults who still stutter face limited options for treatment. Effective management through anxiety control, speech therapy and breathing exercises is the standard course of action.

Because stuttering seemed to run in families, researchers suspected that genetics was involved. Now, they've pinpointed chromosome 12 as the home to these key genetic mutations. Of 123 Pakistani volunteers and 270 American and British volunteers, all of whom stutter, the team determined that many of the volunteers exhibited one of the mutations, which weren't found in a non-stuttering control group.

The results of the study are a welcome myth-buster for those who stutter, because the condition is often blamed on emotional stress or even poor parenting.

"We hear every day from parents worried that they have caused their child's stuttering," Jane Fraser, president of the Stuttering Foundation, said in a statement. "Parents don't cause stuttering, and this research should lift the burden of guilt from their shoulders."

A biological explanation could help mitigate stigma and may also lead to more effective treatment.

"For some patients, there's no real benefit to current therapies," said Dr. Dennis Drayna, lead study author. "Maybe the differences in how patients respond is due to some genetic differences that we can explain."

Pharmaceutical interventions that target cell metabolism, using enzyme replacement therapy, are one option that Drayna wants to see researched further. The treatment is already common among mucolipidosis patients.

Screening at-risk children to institute preventive therapy is another promising possibility.

The genetic discovery is a breakthrough, but it doesn't account for all cases of stuttering. Based on their findings, the team estimates that the three genes explain only 9 percent of genetically related stuttering cases. Now, Drayna said they're pursuing new research to find more.

"We're confident that more than half of stuttering cases can be explained genetically," he said. "With any luck, we'll get our hands on all of them."