First Diagnostic Questionnaire for Assessing Patients’ Social Functioning: Comprehensive DDX3X Syndrome Patient Profile

<b>Background/Objectives:</b> DDX3X syndrome is often misdiagnosed as autism spectrum disorder (ASD, Rett Syndrome, and Dandy-Walker Syndrome). Precise phenotyping is needed with reference to neurodevelopmental diagnosis. Observation of behavior and communication in parents with DDX3X syndrome in the USA, France, and Poland; conversations with the parents of patients; and rudimentary information in evidence-based medical articles prompted us to identify differences in communication, play, and social interaction between children with ASD only, those with both ASD and <i>DDX3X</i>, and those with <i>DDX3X</i> only. <b>Methods:</b> As diagnostic tool for <i>DDX3X</i> patients, we created a questionnaire divided into four sections: medical, social, play, and communication. <b>Results:</b> The results showed inconsistent diagnoses in different countries where children could have been diagnosed with <i>DDX3X</i>. In a comparative analysis, individuals with <i>DDX3X</i> exhibited greater social skills than individuals with ASD. Furthermore, those with <i>DDX3X</i> demonstrated higher levels of social functioning compared to children with ASD. Therefore, parents of children recently diagnosed with ASD or similar conditions are encouraged to complete a survey to determine if their child is likely to have features of DDX3X syndrome. <b>Conclusion:</b> Identification of early behavioral markers that differentiate children with ASD and those with <i>DDX3X</i> could lead to the earliest opportunity for identification and intervention, and can significantly impact developmental trajectories, leading to better long-term outcomes.