Late Diagnosis of Inattentive ADHD in a School-Aged Child Without Hyperactivity: A Comprehensive Therapeutic Approach

Introduction: Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental condition of multifactorial origin, with a strong genetic basis, typically manifesting in childhood and characterized by high clinical heterogeneity. Its impact spans academic, familial, and social domains, and it often coexists with other disorders, complicating detection and management.Objective: To describe a clinical case of late-diagnosed ADHD.Case Presentation: An 11-year-old student, with no history of motor hyperactivity or psychomotor delays, showed adequate early academic performance and lived in a stable family environment. From age 9, attentional difficulties, disorganization, and school-related anxiety emerged, intensifying with increased academic demands. Diagnosis was confirmed through clinical interviews and standardized tools (Conners, BASC-3, DSM-5, Stroop, CPT-3), identifying inattentive-type ADHD. A multimodal treatment was implemented, including cognitive-behavioral therapy (TIMCO model), a gamified educational app, and atomoxetine, resulting in improved task organization, academic performance, and emotional regulation.Conclusions: The late diagnosis of ADHD may be influenced by the absence of motor hyperactivity and a structured environment that masks symptoms. Personalized intervention led to significant functional improvement, highlighting the value of integrative therapeutic strategies tailored to the clinical profile and context.