We report two cases of Brazilian patients (a 22-year-old male and a 48-year-old male) with ischemic stroke, whose arterial vascular study and echocardiographic investigation did not reveal any steno-occlusive arterial disease or typical cardioembolic finding, such as atrial fibrillation or myocardial dysfunction. A transcranial Doppler ultrasound and a transesophageal echocardiogram showed a patent foramen ovale (PFO), and the laboratory screening for coagulation abnormalities showed heterozygosity for MTHFR C677T and A1298C in one of the patients and heterozygosity for factor V Leiden gene mutations in the other patient. The significance of the association of PFO with Methylenetetrahydrofolate (MTHFR) C677T and A1298C variants or factor V Leiden mutation is discussed as a possible cause of ischemic stroke through paradoxical embolism from a venous source. There is a high prevalence of these two mentioned conditions in the general population, so we discuss two cases in which indication for anticoagulant therapy or percutaneous closure of PFO prevails.
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