A case of mixed connective tissue disease complicated with thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is a rare complication of mixed connective tissue disease (MCTD). In this report, we describe the case of a 73-year-old Japanese woman with MCTD who developed fever, thrombocytopenia, and microangiopathic hemolytic anemia and was diagnosed with MCTD together with TTP. The activity of von Willebrand factor (vWF) cleaving metalloprotease ADAMTS13 was low and considered to have contributed to the disease activity of TTP. The patient died despite intensive treatment of plasma exchange (PEX) and steroid pulse therapy. Autopsy results revealed that the kidneys had platelet and fibrin thrombi, which occluded capillaries and arterioles. These findings were compatible with TTP and the decreased activity of ADAMTS13 was considered to be associated with the disease activity of TTP.