The aim of this study is to determine the frequency of cardiac and cerebral involvements in patients with idiopathic thrombotic microangiopathies on diagnosis. Patients will be assessed for cardiac involvement (troponin Ic level and cardiac ultrasonography) and cerebral involvement (cerebral MRI). The investigators will assess whether serum troponin Ic on diagnosis can predict morbidity and mortality of patients with a thrombotic microangiopathy at the acute phase.