Early Predictors of Later Expressive Language in Boys With Fragile X Syndrome.

The predictive ability of early consonant inventory and intentional communication on later expressive language was examined in 36 boys with fragile X syndrome (FXS). Autism symptom severity was included as a potential moderator. Participants were visited in their homes twice over a 6-year period, and mother-child interactions were videotaped, coded, and transcribed behavior by behavior. Consonant inventory and concurrent autism symptom severity were predictive of later number of different words, as was the interaction between the two. Intentional communication was not predictive of number of different words. These findings provide additional specific evidence for differences in foundational language abilities associated with autism symptom severity in boys with FXS. Clinical implications are discussed.