Clozapine has anti-aggressive effects independent of improvement of psychosis and reduce aggression, agitation and selfinjurious behavior. Among individuals with intellectual disabilities (ID) and comorbid psychiatric illness, clozapine is increasingly being prescribed to treat behavioral disturbances.

We report a case of clozapine rechallenge after neutropenia in a 30-year-old patient affected by intellectual disability and psychotic disorder with disruptive behavior.

After several failed trials of other antipsychotics, the patient required an inpatient stabilization. Clozapine was prescribed to manage his severe set of psychotic symptoms and behavioral disturbances. At baseline the full blood count was normal. The patient responded to clozapine and the dose was rapidly increased until it was 300 mg/day. After ten days, a white blood cell (WBC) count of 3.50 migl/mmc and a neutrophil count of 1.56 migl/mmc were revealed. Clozapine was withdrawn. During the following three months the patient had been treated with several combinations of antipsychotics, mood stabilizers and benzodiazepines, but he continued to exhibit bizarre behavior, severe paranoid delusions, and an inability to conduct activities of daily living. Therefore, after a brief period of washout, clozapine was reinstated (25 mg/day) and it was slowly increased by 25 mg every week until it was 100 mg/day. The patient improved and his WBC count and absolute neutrophil count remained within normal limits. Clozapine might be an effective treatment option for individuals with ID and psychotic disorder whose symptoms are not adequately controlled. Furthermore, we assume that a slow titration might help in preventing neutropenia during clozapine rechallenging.