A Note on Genetics and Childhood Apraxia of Speech

 

As far as the general norm goes, the human being has 23 pairs of chromosomes, one from each parent. These chromosomes are packed with proteins called DNA. DNA is organized into sections on these chromosomes, called genes. Genes are made up of specific proteins that do specific things (ie expression) that are essential to the fundamentals of everything from the color of our hair, to the beating of our hearts, and even to the speech and sounds that we utter. It has been discovered that a certain protein on a certain gene is responsible for the expression of speech and language.

Childhood Apraxia of Speech (Also known as “Developmental Verbal Dyspraxia” in the UK), has been found to have, in some instances, a known genetic mutation of a gene called “FOXP2”, (Forkhead Box P2), which is a protein that is encoded by the gene of the same name. FOXP2 has been found to be required for the normal development of Speech and Language. This discovery was made in the study of a well known British family (KE). The gene has been localized to an area on Chromosome 7, in the region of 7q31 at the SPCH 1 locus. FOX P2 is expressed in the brain and other areas of the human body such as the lungs and the gut. By studying this family pedigree in which three generations of family members had a severe speech sound disorder diagnosed as “Developmental Verbal Dyspraxia”, researchers found a mutation on one of the proteins on the FOXP2 gene. They concluded that the FOXP2 gene is implicated in Childhood Apraxia of Speech.

Another study showed two patients with CAS had a deletion at another chromosome (16p11.2).

What this implies is that there is strong genetic basis for Childhood Apraxia of Speech, although it is not yet certain if this applies to all children with Idiopathic Childhood Apraxia of Speech. Certainly in cases like Fragile X, Galactosemia and other known genetic disorders, CAS seems to have the genetic association.

The question arises then, What is the role of Genetic Testing in Children with Childhood Apraxia of Speech?

It is important to understand that knowing what and which gene is involved does not alter the treatment plan for Childhood Apraxia of Speech. Intensive Speech therapy will still be needed regardless of the genetic basis for it if present. In children in whom there are other medical or developmental problems, it would be helpful to do genetic testing to help identify the diagnosis and then look for other features of a particular syndrome if present. But, in otherwise healthy children in whom Childhood Apraxia of Speech seems to be the only feature, parents should strongly weigh the pros and cons of doing genetic testing, taking the costs of such test vs whether the information gained will make any difference to  or alter the treatment of their child. A talk with your child’s pediatrician would be the ideal way to approach this topic and come to any decision. Your child’s pediatrician might suggest that testing is warranted, as it is in certain cases, or might present the argument for not doing any testing. Either way, it should be an informed decision.

Read more at Apraxia-KIDS.org/Genetics

The Purpose of Genetic Testing and It’s Relevance, Heidi Feldman, MD.

References:

Kay D. MacDermot,1,2 Elena Bonora,1,* Nuala Sykes,1 Anne-Marie Coupe,1 Cecilia S. L. Lai,1,† Sonja C. Vernes,1 Faraneh Vargha-Khadem,3 Fiona McKenzie,4 Robert L. Smith,4 Anthony P. Monaco,1 and Simon E. Fisher1Identification of FOXP2 Truncation as a Novel Cause of Developmental Speech and Language Deficits,Am J Hum Genet. 2005 Jun; 76(6): 1074–1080.Pubmed
Lai CS1, Fisher SE, Hurst JA, Vargha-Khadem F, Monaco APA forkhead-domain gene is mutated in a severe speech and language disorder. PubMed Absract
Vargha-Khadem F1, Gadian DG, Copp A, Mishkin M.Nat Rev Neurosci. 2005 Feb;6(2):131-8. FOXP2 and the neuroanatomy of speech and language. PubMed Abstract
Raca G, Baas, B.S. et al, Childhood Apraxia of Speech (CAS) in two patients with 16p11.2 microdeletion syndrome. European Journal of Human Genetics (2013) Vol 21, 455-459.