Patient: Female, 21-year-old Final Diagnosis: Toxocariasis-associated acute perimyocarditis with cardiogenic shock Symptoms: Dizziness • epigastric pain • headache • vomiting Medication: — Clinical Procedure: — Specialty: Cardiology Objective: Rare disease Background: Toxocariasis is an infection due to ingestion of the helminth parasite larvae found in dogs ( Toxocara canis ) or cats ( Toxocara cati ). Symptoms vary from being asymptomatic to shock, depending on the organ invaded by the parasite. However, cardiac involvement with shock in toxocariasis is very rare. Case Report: A 21-year-old woman without any history of underlying conditions visited the Emergency Department because of epigastric pain, vomiting, headache, and dizziness. Her blood pressure was 80/60 mmHg. Computed tomography (CT) of the brain showed no abnormal lesions. The abdominal-pelvic CT with contrast showed right pleural effusion, pericardial effusion, and focal ascites in the pelvic cavity. Laboratory tests revealed an elevation of eosinophils (40%) and cardiac enzymes (creatinine kinase-MB 27.6 ng/mL, high-sensitive cardiac troponin T 1.21 ng/mL). The transthoracic echocardiogram showed left ventricular systolic dysfunction (ejection fraction 44%) and moderate pericardial effusion. She was presumptively diagnosed with hypereosinophilic perimyocarditis and admitted to the Intensive Care Unit for shock. The pericardial effusion increased during treatment; therefore, pericardiocentesis was performed. Analysis of the pericardial effusion showed eosinophilia (eosinophils 90%) and the serologic test for parasites was positive for Toxocara and Sparganum . A combination therapy of albendazole, praziquantel, and corticosteroid resolved the pericardial effusion and the peripheral blood eosinophil count normalized. She was discharged without any other complications. At Outpatient Clinic follow-ups and observations over the next 2 years there were no abnormal findings, including pericardial effusion or eosinophilia. Conclusions: Toxocariasis rarely causes perimyocarditis with cardiogenic shock. Patients who present with pericardial effusion and eosinophilia need to be evaluated for parasitic infection.