A role for inherited metabolic deficits in persistent developmental stuttering

► Linkage studies are rapidly identifying new loci for stuttering. ► To date mutations in GNPTAB, GNPTG, and NAGPA have been associated with stuttering. ► These genes encode the lysosomal enzyme targeting pathway, defective in mucolipidosis. ► Stuttering individuals studied to date showed no symptoms of mucolipidosis. ► Deficits in intracellular trafficking and reduced enzyme half-life are present.