Abstract Backgound: Cardiac amyloidosis is associated with an increased thromboembolic risk. While the need to anticoagulate patients in atrial fibrillation regardless of the CHA2DS2–VASc score is evident, it is not clear whether and which patients in sinus rhythm should be treated with anticoagulant drugs Case Presentation A 51–year–old man presented with repeated episodes of chest pain and exertional dyspnea. The ECG showed synus rhythm, left–axis deviation, 1st degree AV–block, left anterior hemiblock and no significant anomalies of ventricular repolarisation. Transthoracic echocardiography revealed markedly thickened left ventricular (IN) walls (maximum interventricular septum dimension 18 mm) with a granular–sparkling appearance of the myocardium, bi–atrial enlargement, preserved LV ejection fraction (EF 52%), restrictive mitral flow pattern with a very small A–wave, thickened interatrial septum and atrio– ventricular valves; circumferential pericardial effusion ( maximum 11mm). Laboratory tests showed an increase in troponin and NTproBNP levels and serum and urine immunoelectrophoresis showed a monoclonal component in zone kappa. A periumbilical fat biopsy was negative for amyloidosis so the patient underwent an endomyocardial biopsy which showed positive Congo red, and immunohistochemistry positive for kappa light chains and negative for transthyretin. A diagnosis of cardiac amyloidosis AL was then made and the patient was referred to the hematologist to perform specific therapy. One week after discharge he was hospitalized for acute pain in the lower limbs due to acute thrombosis of the left common femoral artery treated with Fogarty embolectomy. Discharged in therapy with low molecular weight heparin after a few days he was again symptomatic for pain in the lower limbs and went to the emergency room where he died of electromechanical dissociation. Conclusions Our case demonstrates that cardiac AL amyloidosis is associated with an increased thromboembolic risk, irrespective of the presence of atrial fibrillation, for the hematological disease itself and for the infiltration of the atrium by the amyloid substance. This suggests that in selected cases, with reduced A–wave amplitude and evidence of impaired atrial mechanics, empirical anticoagulation should be considered even in sinus rhythm.