We present a 38-year-old female patient on peritoneal dialysis for 3 years due to mesangioproliferative glomerulonephritis since early adolescence and chronic failure of the right kidney transplants. In early 2006 she was treated with high-dose cortisone due to cryptogenic, organized pneumonia. During a routine echocardiographic examination performed because of occurrence of cerebral symptoms such as diminished visual and auditory acuity in the patient, we detected a mobile, left ventricular thrombus of unusual large size, along with serologically measured Lupus anticoagulant antibodies (LA). The thrombus could be completely lyzed within only 12 hours by urokinese and antithrombotic danaparoid sodium therapy without surgical intervention. Successful treatment was proven by negative LA antibody activity as well as by echocardiography. The general clinical health was greatly improved after rehabilitation 2 months after lysis. We assume that the patient may have had infection- or cortisone-triggered transitory LA antibodies causing the serious heart thrombus with hypokinesia in the apex cordis.