Psychosis and Incidental Latent Toxoplasmosis: A Case Report and Key Learning Points

Psychotic disorders are characterized by hallucinations, delusions, and impairments in reality testing, with relapses often associated with medication non-compliance, psychiatric stressors, and substance use. Toxoplasma gondii is a neurotropic intracellular parasite with a high global seroprevalence, and latent infection has been documented in association with psychotic syndromes, although the nature of this relationship remains uncertain. The aim of this case report is to describe a patient presenting with a psychotic relapse in whom latent Toxoplasma gondii infection was identified during inpatient investigation. This is a case of a 37-year-old woman who presented to the emergency department with a severe psychotic relapse on a background characterized by persecutory delusions, sexual misinterpretations, multimodal hallucinations (including visual phenomena), and substantial functional deterioration. Her psychiatric history included a background of unspecified primary psychosis with multiple admissions due to psychotic relapses, substance misuse (alcohol and amphetamines), and periods of disengagement with mental health services. During admission, a palpable cervical nodule was identified, prompting further investigations, which revealed previous exposure to Toxoplasma gondii. Routine physical examination revealed a palpable cervical nodule, and given the context of cat exposure, serological examination was ordered. This revealed a latent Toxoplasma gondii infection (IgG positive, IgM negative). She did not have any neurological features consistent with toxoplasmic encephalitis and did not require antiparasitic therapy. Recent use of stimulants and alcohol use before admission were acknowledged. She was started on oral risperidone and then transitioned to paliperidone palmitate on account of symptom severity and concerns about adherence. She significantly improved, with complete resolution of psychotic symptoms. She was discharged on depot treatment, with continued community support. This case illustrates caution in interpreting incidental findings in complex psychotic manifestations. Even though associations between latent Toxoplasma gondii and psychosis have been documented, the nature of this relationship remains uncertain. This case highlights the need to interpret a past Toxoplasma gondii infection with caution and the importance of considering contributing factors such as substance misuse and psychosocial stressors.