DOI: https://doi.org/10.36347/sjmcr.2026.v14i08.010

Pages: 1800-1806

Background: Hematological adverse reactions associated with second-generation antipsychotics (SGAs), other than clozapine, are uncommon. Recurrent neutropenia following sequential exposure to different SGAs is exceptionally rare and has been described almost exclusively in isolated case reports. We report the case of an adolescent with autism spectrum disorder (ASD) who developed neutropenia during risperidone treatment, followed by further deterioration after switching to quetiapine. Case presentation: A 17-year-old adolescent with ASD experienced worsening behavioral symptoms, leading to gradual titration of risperidone up to 6 mg/day. Routine hematological monitoring revealed leukopenia associated with neutropenia, prompting dose reduction followed by treatment discontinuation because of progressive hematological abnormalities. Neutropenia persisted despite risperidone withdrawal. Owing to persistent severe behavioral symptoms, quetiapine was initiated. Although an initial improvement in neutrophil count was observed, dose escalation was followed by a progressive decline in the absolute neutrophil count, reaching a nadir of 0.51 × 10⁹/L, which required discontinuation of quetiapine. A comprehensive etiological work-up (bone marrow aspirate, bone marrow biopsy, vitamin panel, viral serologies, autoimmune panel) failed to identify an alternative etiology, although pre-existing chronic neutropenia, particularly benign ethnic neutropenia, could not be definitively excluded. Causality assessment using the French Bégaud method (intrinsic imputability: I1–I2) and the Naranjo Adverse Drug Reaction Probability Scale (score = 6) supported a probable causal relationship. Conclusion: This case highlights the rare occurrence of sequential neutropenia associated with two different second-generation antipsychotics in the same patient. It emphasizes the importance of careful hematological monitoring in patients who develop blood dyscrasias during antipsychotic treatment, particu