[Beyond words: The complexity of differential diagnosis and treatment of severe ritualized behaviors in an autistic adolescent without functional language and with an intellectual disability: A case report].

Autistic youth diagnosed with an associated intellectual disability (ID) represent nearly one third of the autistic population. However, the majority of studies on mental health and autism focus on autistic individuals without ID. Therefore, the mental health needs of autistic youth with an ID are still poorly understood. This case report focuses on the psychiatry follow-up of Nabil (fictitious name), an autistic adolescent with ID who has been treated for nearly 10 years for various symptoms, including ritualized behaviors that are part of a complex and rare diagnostic profile. In terms of neurodevelopmental disorders, in addition to symptoms associated with autism and ID, a diagnosis of attention deficit/hyperactivity disorder (ADHD) and Tourette syndrome was made, but the ADHD diagnosis was not maintained. Catatonia associated with autism has also emerged and is currently in remission. In terms of mental health, a diagnosis of obsessive-compulsive disorder (OCD) was made and behavioral problems were noted, without being attributed to the previous diagnoses. The presented case has three specific objectives: 1-to illustrate the challenges inherent in assessing the intellectual potential of autistic individuals with very low adaptive functioning and the impact on the treatment; 2- to provide avenues for the differential diagnosis of autistic rituals, compulsions, tics, stereotypies, and ADHD within this population and 3- to raise awareness about the underdiagnosis of catatonia in autistic youth.