Adolescent-onset delusional disorder: two case reports illustrating diagnostic complexity and phenomenological overlap

Delusional disorder is rare in adolescence and may be difficult to recognize due to non-bizarre symptom content and relatively preserved overall functioning. Its phenomenological overlap with other psychiatric conditions may further complicate diagnostic formulation during this developmental period. As a result, diagnosis is often delayed, and initial clinical contact frequently occurs outside psychiatric settings. Reporting adolescent cases is important to increase clinical awareness, highlight diagnostic challenges, and illustrate the heterogeneity of presentation during this developmental period. We report two adolescents admitted to a Child and Adolescent Psychiatry Unit who presented with prominent delusional and delusion-like beliefs. The first case involved a 14-year-old girl presenting with erotomanic delusions centered on a former teacher, accompanied by secondary persecutory and referential ideas and delusional misidentification phenomena. The second case concerned a 15-year-old boy with fixed somatic beliefs regarding his skin color, emerging in the context of prominent body dysmorphic symptoms and severe anxiety, culminating in a suicide attempt. In both cases, core features of schizophrenia were absent, and functioning outside the delusional context was relatively preserved. Treatment included pharmacological interventions with second-generation antipsychotics, alongside psychotherapeutic and family-based approaches. Clinical improvement was observed in both patients, although treatment response and clinical course differed markedly. These cases illustrate the diagnostic complexity of prominent delusional and delusion-like beliefs in adolescence, including the phenomenological overlap between delusional disorder and body dysmorphic disorder. Careful phenomenological assessment, particularly of the content, conviction, insight, and functional impact of beliefs, as well as attention to comorbidities and developmental context, is essential for accurate diagnosis. Increased clinical awareness may support earlier recognition, improve therapeutic engagement, and help preserve psychosocial functioning.