Recent-Onset Catatonia in Severe Autism Revealing Type 1 Diabetes and Multifocal Thromboembolism: A Pediatric Case Report

Introduction: Catatonia may occur in Autism Spectrum Disorder (ASD), yet in severe nonverbal autism, it is frequently underrecognized because catatonic features can overlap with baseline autistic behaviors. This diagnostic challenge is clinically important, as recent-onset catatonia may signal a life-threatening underlying medical disorder. The present case was managed in a university hospital in southern Tunisia during the summer of 2025. Catatonia was diagnosed according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) criteria, and severity was serially assessed using the Pediatric Catatonia Rating Scale (PCRS). Case Presentation: A 14-year-old nonverbal girl with DSM-5-TR ASD level 3 and intellectual disability presented with a 1-month marked change from baseline, characterized by paradoxical agitation, unusually severe aggressive outbursts, profound insomnia, markedly increased stereotypies, and new posturing. After receiving a very low dose of periciazine (2 mg), she developed paradoxical intolerance with a fall and diffuse muscle contracture. Emergency reassessment identified multiple DSM-5-TR catatonic signs superimposed on her autistic baseline, including psychomotor slowing, abnormal posturing, orobuccal grimacing, echopraxia, worsening stereotypies, and paradoxical agitation poorly modulated by external stimuli. Her initial PCRS score was 27. A somatic-first work-up revealed new-onset type 1 diabetes with diabetic ketoacidosis and multifocal thromboembolism, including axillary vein thrombosis and bilateral pulmonary embolism, related to congenital protein C deficiency. The final diagnosis was catatonia due to another medical condition. Treatment consisted of insulin therapy, rehydration, electrolyte correction, anticoagulation, and supportive care, without benzodiazepines, antipsychotics, or electroconvulsive therapy. Clinical improvement paralleled medical stabilization, with PCRS scores decreasing from 27 at presentation to 16 after 48 hours and to 8 at discharge, with sustained improvement at 2-month follow-up. Conclusion: In autistic youth, an abrupt departure from baseline should prompt urgent assessment for catatonia and an immediate medical work-up to identify the underlying cause. Paradoxical sensitivity to even very low-dose first-generation antipsychotics may be an additional warning sign. Serial standardized ratings may help document recovery and support remission with treatment of the underlying medical condition alone.