Many studies reported the presence of language impairments in children and adolescents with Klinefelter syndrome (KS). However, the first stage of their language development has been scarcely studied. The present study aimed to describe the spontaneous communicative production of 18-month-old children with KS, in comparison with that of typically developing (TD) male peers, aiming to verify the existence of different early communicative skills in both vocal and gestural modality and to identify the presence of possible associations with their later vocabulary size. Children with KS showed a lower competence in both lexical skills and emergent syntactic abilities than TD peers. No significant differences were found in gesture production. Considering the possibility of identifying an association between early communicative skills and later vocabulary size, the vocal production of TD children appeared to be significantly related to their later lexical skills; whereas, the number of gestures produced by children with KS appeared to be related to their later lexical abilities. The early detection of language risk factors will allow early intervention and careful monitoring of these children's communicative development.

Individuals with sex chromosome trisomies (SCTs) have an increased risk of language delays and impairments. However, there are only a few data relative to their language development in early childhood. The present study aimed to investigate the preverbal skills shown by a group of 8-month-old children with SCTs to assess the presence of a possible early communicative delay. Moreover, the predictive role of early preverbal productions on later lexical development at 24 months was analysed. Twenty-six children with SCTs and 24 typically developing (TD) children participated in the study. Their use of vocal productions and gazes addressed to the communicative partner was assessed during a parent–child observation session held when the children were 8 months old. In addition, the children’s word comprehension at 8 months and their word production at 24 months were indirectly assessed by a parental report. Children’s word comprehension was similar in the two groups of children, whereas a significantly lower frequency per minute of gazes was found in children with SCTs than in TD children. A significantly lower proportion of children with SCTs showed the ability to produce babbling during the observation session, and significant differences were also found in the frequency of babbling utterances. No significant differences emerged among the subgroups of children with different types of SCTs. The predictive role of babbling on later lexical size was found in TD children but not in children with SCTs. This result could be probably explained by the small number of children in this group who could produce babbling utterances. The study leads to identify early signals of delay in the preverbal skills of children with SCTs. Early monitoring of their communicative development could help the clinicians in intervening with well-timed and targeted programmes.