1. Understanding the genetic mechanisms of any disorder is basic science that can then lead to clinical applications.
2. Some disorders including speech sound disorder may have distinct subtypes that, on the surface, resemble each other but that are caused by different genes. A better understanding of the genetic causes can lead to a biologically defined subtype system. Such a subtype system would contribute greatly to current thinking about speech sound disorder, as at present, no universally accepted subtype system exists.
3. Knowing the genetic etiology of speech sound disorder subtypes can greatly increase diagnostic accuracy when determining the presence and nature of a speech problem in a young child.
4. Knowing whether a very young child is at risk of developing speech sound disorder can guide decisions regarding early intervention, which can greatly improve the chances of early normalization. Too many times, parents and health care providers take a wait-and-see approach when a child does not produce at least some comprehensible speech by age 2 years. By this time, early speech intervention could have already been effective in addressing the disorder.
5. Okay, let’s imagine that we identify a gene that causes speech sound disorder in a subset of families whose children struggle with speech. What’s next? We would want to know what the gene’s function is, how it is expressed in different body tissues, and how it is functionally related to other genes via transcription factors. Research in the genetics of an epilepsy subtype has shown that an understanding of a causal gene’s function can be used to design drugs that counter the effects of the epilepsy (Catterall, Kalume, & Oakley, 2010). This work has not yet been applied to humans, but it is theoretically possible that pharmacogenetics may become an active field of research and clinical application even for communication disorders such as speech sound disorder.
Catterall, W. A., Kalume, F., & Oakley, J. C. (2010). NaV1.1 channels and epilepsy. J Physiol, 588(Pt 11), 1849-1859.