Face aux symptômes psychotiques chez l’enfant et l’adolescent, les diagnostics peuvent varier d’un centre de soin à l’autre, de schizophrénie à début précoce, pour les classifications internationales (DSM-5), à la dysharmonie multiple et complexe du développement (MCDD) ou dysharmonie psychotique pour les classifications françaises (CFTMEA R-2020). Nous avons choisi d’évoquer le parallélisme symptomatologique entre ces troubles mentaux et leur place respective dans les classifications françaises et internationales et la pratique clinique. Nous mettons également en évidence un de leurs symptômes communs, à savoir la distorsion de la représentation du corps et du schéma corporel, ainsi que son rôle dans l’émergence et le maintien de la symptomatologie. Enfin, nous expliquons en quoi l’évaluation et la réadaptation du schéma corporel est un outil diagnostique intéressant pour la prise en charge des enfants et des adolescents présentant des symptômes psychotiques. En effet, dans le cadre de la détection des troubles psychotiques, cette évaluation du schéma corporel semble d’autant plus cruciale que des anomalies apparaissent lors des phases prodromiques, notamment dans la schizophrénie, phases encore peu accessibles aux outils diagnostiques existants.

This article explores the variability of diagnostic approaches to psychotic symptoms in children and adolescents, focusing on the concept of body schema distortion as a transdiagnostic marker within the schizophrenia spectrum and related developmental disorders. We argue for the clinical utility of assessing body schema as both a diagnostic and therapeutic tool, particularly in the early detection of psychosis, where traditional diagnostic methods may fall short. Diagnoses of childhood psychosis remain heterogeneous depending on the clinical framework employed. International classifications such as the DSM-5 typically refer to early-onset schizophrenia and very early-onset schizophrenia, while the French psychiatric classification, such as the CFTMEA R-2020, include entities like multiple and complex developmental disorders and psychotic disharmony. These differing taxonomies may reflect a broader divergence in conceptualizing the nature and progression of early psychotic disorders. First, we wanted outlining diagnostic criteria for early onset schizophrenia, noting that these conditions are characterized by hallucinations, delusions, disorganized speech or behavior, and negative symptoms such as affective flattening and social withdrawal. In children, symptoms often emerge more insidiously, with a higher prevalence of auditory hallucinations and negative symptoms. The presence of anosognosia and somatic concerns is also common. We then discuss about Multiple and Complex Developmental Disorders and Psychotic Disharmony; commonly used in French child psychiatry. Multiple and Complex Developmental Disorders describes children with developmental delays across various domains, emotional dysregulation, and thought discontinuities without reaching the full criteria for schizophrenia. Psychotic disharmony, defined in the CFTMEA, highlights developmental asynchrony involving language, motor skills, and affect regulation, often accompanied by intense anxiety and perceptual distortions. These syndromes present early in life and are characterized by fluctuating clinical presentations over time. Despite some overlapping features with schizophrenia, they are conceptualized as distinct entities with different developmental trajectories. One of the article's central contributions is the proposition that distortions in body representation, particularly in the non-conscious, sensorimotor construct known as the body schema, may constitute a core symptom across these diagnoses. Body schema refers to the brain's automatic and continuously updated representation of bodily posture and movement. It integrates sensory inputs from proprioception, vision, and balance, and is primarily processed in parietal and insular brain regions. In both schizophrenia and psychotic disharmony, disruptions in this schema are thought to contribute significantly to clinical symptoms. In schizophrenia, patients frequently exhibit abnormal multisensory integration, particularly in interoception and proprioception, which can manifest as altered awareness of heartbeat, respiration, or muscle tension. This disruption is linked to dysfunctions in the insular cortex and parietal lobe. Moreover, schizophrenia patients often display increased susceptibility to perceptual illusions, such as the rubber hand illusion, suggesting a more malleable and externally anchored sense of bodily self. This over-reliance on external sensory cues may undermine a stable internal model of the body, contributing to symptoms like delusions, hallucinations, and disorganized thought. These distortions also impact motor control, diminishing the ability to correctly attribute agency to one's own actions. This impaired sense of motor ownership is thought to be fundamental to the disintegration of self-perception and social cognition observed in schizophrenia. Particularly in early-onset forms, where the bodily self is still developing, these deficits may interfere with the child's emerging sense of identity and interpersonal boundaries. A similar framework is applied to psychotic disharmony, where disruptions in the body schema are interpreted through psychodynamic concepts such as the “Moi-Peau” (which can be literally translated as “skin ego”), which functions as a psychological boundary between the self and the environment. Children with psychotic disharmony often struggle to construct a coherent bodily identity, leading to experiences of bodily porosity, undifferentiation from others, and overwhelming anxiety. These children may resort to compensatory mechanisms: such as motor stereotypes or somatic fixations to manage these internal instabilities, albeit ineffectively. We finally argue that evaluating body schema distortions can aid early detection of psychotic disorders, particularly during prodromal phases. In schizophrenia, these alterations often precede the full emergence of psychotic symptoms, highlighting their potential as early markers. A systematic assessment of body schema could complement conventional diagnostic methods and help identify children at high risk for developing psychosis. Furthermore, in complex cases of differential diagnosis, we suggest that body schema assessment may assist in differentiating schizophrenia from other developmental conditions like autism spectrum disorders. Although both conditions involve atypical body representation, their signatures differ: individuals with autism spectrum disorders generally exhibit a more rigid and under-dimensioned body schema, in contrast to the more labile and over-dimensioned schema observed in schizophrenia. Such distinctions could refine diagnostic accuracy and inform tailored interventions. The conclusion emphasizes the transdiagnostic relevance of body schema assessment in child and adolescent psychiatry. We propose that, regardless of diagnostic label (schizophrenia, multiple and complex developmental disorders, or psychotic disharmony) evaluating disturbances in bodily representation can facilitate communication among clinical teams, support diagnostic reasoning, and guide personalized care strategies. The body schema thus emerges as a unifying construct that bridges divergent nosographic frameworks and offers a valuable tool for early identification and treatment planning in pediatric psychosis.