Endothelial Dysfunction in a Patient With Post-COVID-19 Syndrome and Mutation of the MTHFR Gene and Prothrombin II.

Post-COVID-19 syndrome (also known as long COVID) is defined as the persistence of cardiovascular symptoms (chest pain, fatigue, palpitations) 12 weeks after the acute phase of SARS-CoV-2 infection. SARS-CoV-2 has been shown to directly infect endothelial cells through ACE2 receptors, leading to endotheliitis and vascular inflammation. In susceptible individuals, this endothelial damage may persist after viral clearance, contributing to coronary microvascular dysfunction. Genetic predispositions (primary thrombophilias) may further aggravate endothelial injury. The prothrombin factor II G20210A mutation has been associated with an increased risk of venous and arterial thrombotic events. The MTHFR gene mutation, particularly the homozygous C677T polymorphism, is associated with reduced activity of methylenetetrahydrofolate reductase, impairing the conversion of homocysteine to methionine. This leads to hyperhomocysteinemia, which contributes to endothelial dysfunction (ED). We report the case of a 25-year-old Mexican woman with a four-month history of chest pain and dyspnea (following a previous COVID-19 infection associated with vaccination). She presented with acute chest pain and dyspnea requiring hospitalization. Echocardiography revealed abnormal regional longitudinal strain in the basal anteroseptal wall (-7%) and basal-mid anterolateral wall (-14% and -16%, respectively), with reduced myocardial work in basal and mid-segments (379-1715 mmHg%). Cardiac magnetic resonance imaging (CMRI) demonstrated myocardial involvement; however, coronary CT angiography (CCTA) excluded obstructive disease. Anti-SARS-CoV-2 IgG levels were markedly elevated (2893 AU/mL). Hematologic evaluation revealed abnormal platelet aggregation with platelet hyperreactivity and the identification of homozygous MTHFR C677T and heterozygous prothrombin factor II G20210A mutations. The patient initially received prophylactic anticoagulation with apixaban during hospitalization, which was discontinued after discharge. Long-term treatment included low-dose aspirin, folic acid, B-complex vitamins, bisoprolol, and trimetazidine for angina control. At a one-year follow-up, the patient showed clinical improvement, with a reduction in the frequency and intensity of angina. This case suggests that patients with platelet hyperreactivity, MTHFR (C677T), and prothrombin factor II (G20210A) mutations may be predisposed to developing ED and coronary microcirculatory impairment following SARS-CoV-2 infection in post-COVID-19 syndrome. We address the use of prophylactic anticoagulants in selected cases such as ours, which, although not specifically recommended by current guidelines (American Society of Hematology), may be considered after an individualized risk-benefit assessment.