Simultaneous Onset of Schizophrenia in Two Sisters: A Case Report

Abstract

Introduction: Family, adoption, and twin studies have consistently demonstrated a strong heritable component of schizophrenia, with a significantly increased relative risk among first-degree relatives of patients with schizophrenia. The simultaneous onset of schizophrenia among family members is uncommon but clinically significant. Case Presentation: Two sisters aged 32 and 25 years, with no psychiatric history, were admitted for severe aggression and psychotic symptoms that began after family stressors. Both developed grandiose, persecutory, and bizarre delusions, including a prophetic identity, supernatural pregnancies, vast inheritances, and Capgras syndrome, in which they believed their parents were impostors. The younger sister also experienced auditory and visual hallucinations. Physical examination and laboratory findings were normal. Despite treatment with risperidone, haloperidol, and six electroconvulsive therapy sessions, no improvement was observed until clozapine was initiated, leading to a marked reduction in delusions and aggression. Both sisters were discharged on clozapine 150 mg/day and maintained remission at the six-month follow-up. Conclusions: Genetic predisposition and shared stressors may have contributed to schizophrenia in two sisters. Similar symptoms and persistent psychosis after separation supported independent diagnoses rather than an induced psychosis. This case highlights the importance of careful diagnosis, early identification of treatment resistance, and prompt initiation of clozapine in refractory cases. Familial clusters of psychosis illustrate how biological vulnerability may be exacerbated by isolation and enmeshment.