Mobile right heart thrombus as a manifestation of homozygous mutation of MTHFR 1298 A>C.

Mobile right heart thrombus (MRHT) is uncommon pathology but the true prevalence is still unknown. Previous studies reported that MRHT occurs in 7% to 18% of patients with pulmonary embolism with high mortality rate (44.7%) (1). The main manifestations of venous thromboembolism (VTE) are deep venous thrombosis (DVT) and pulmonary embolism. In addition, genetic factors play an important role in pathogenesis of VTE. The relationship between common genetic mutations such as factor V Leiden, prothrombin factor II G 20210A, methylenetetrahydrofolate reductase (MTHFR), deficiencies of protein C, protein S, and antithrombin III, and VTE have been reported (2). A 34-year-old man admitted to the emergency department because of sudden onset of dyspnea. He had no previous history of both VTE and acute coronary syndrome. He denied any trauma, history of malignancy, recent surgery, and any drug usage. Only 10 days before, he had fracture of toe, which did not require plaster cast and immobilization. Admission physical examination was unremarkable. Baseline 12-lead electrocardiogram (ECG) revealed sinus rhythm and S1Q3T3 sign. Duplex scan of the lower extremities was also normal. Because of suspicion of pulmonary embolism, bedside transthoracic echocardiography (TTE) was performed, which revealed mobile right atrial mass. Left ventricular ejection fraction was normal (60%). Right ventricle was not enlarged and estimated systolic pulmonary arterial pressure was 28 mmHg. Because of poor imaging quality with TTE, transesophageal echocardiography (TEE) was performed and two hypermobile and snake-like thrombi in the right atrium were demonstrated (Fig. 1 and Video 1. See corresponding video/movie images at www.anakarder. com). Laboratory parameters were within normal limits. Protein C and S levels were also normal. Homocysteine was slightly elevated: 19.6 μmol/L (5.5-14 μmol/L). Upon genetic testing, there were no mutations in the factor V Leiden (G1691A), factor II (G20210A), and MTHFR (C677T). Only homozygous mutation of MTHFR (A1298C) was detected. Pulmonary computed tomography angiography revealed bilateral lower lobe pulmonary embolism (Fig. 2). Because of hemodynamic stability and no evidence of RV strain, anticoagulation with heparin was started. After 10 days of hospitalization, control TEE was performed and right atrial thrombi were markedly decreased (Fig. 3 and Video 2. See corresponding video/movie images at www.anakarder.com). The patient was discharged with warfarin treatment for indefinite time. The relationship between both C677T and A1298C polymorphisms of the MTHFR gene and VTE have been analyzed before (3). However, there are conflicting results regarding the role of MTHFR gene mutation in VTE pathogenesis (4). In cases of homozygous MTHFR mutations, hyperhomocysteinemia may occur. The relationship between hyperhomocysteinemia and VTE is still unknown and conflicting results are present. Auerbach et al. (5) have reported that homozygous MTHFR mutation that leads to hyperhomocysteinemia can increase the risk of VTE up to 2.5-folds. Therefore, in the present case, we postulated that the possible cause of right atrial thrombi is MTHFR A1298C homozygous mutation because no other predisposing factors were present in our patient. In addition, previous cases of VTE were presented with heterozygous MTHFR mutation. However, our patient had homozygous MTHFR mutation and, right heart thrombus as a manifestation of homozygous