Dyslexia more severe if two genes affected

The consequences of dyslexia, a reading disorder that affects as much as 17 percent of the population, can be greatly minimized by early educational intervention. Because the condition has a strong genetic component, researchers have been eager to develop a genetic test to identify children at risk at as young an age as possible.

In 2005, a team led by Jeffrey R. Gruen, M.D., linked variations in a gene called DCDC2 to dyslexia risk, and other researchers made a similar connection between dyslexia and a gene known as KIAA0319. In a new study, published on July 11 in The American Journal of Human Genetics, Gruen and colleagues found that children carrying variations in both genes scored significantly lower on tests of reading and other language skills than those with variations in one or the other.

The robustness of the effect on test scores of this genetic double-whammy could provide the basis for a reliable and practical genetic screen, which is sorely needed, says Gruen: “Research shows that if children with dyslexia receive intensive intervention before middle school, 75 percent will be reading at grade level even two years after completing it. Testing for both DCDC2 and KIAA0319 variants could identify the children who would benefit most from intervention.”