Malignancy-Associated Microangiopathic Hemolytic Anemia Mimicking Thrombotic Thrombocytopenic Purpura in a Patient With Metastatic Breast Cancer: A Case Report.

Microangiopathic hemolytic anemia (MAHA) is a form of Coombs-negative hemolysis characterized by mechanical fragmentation of erythrocytes, producing schistocytes on the peripheral blood smear. When accompanied by thrombocytopenia and neurological features, the presentation closely resembles thrombotic thrombocytopenic purpura (TTP), a hematological emergency requiring urgent plasma exchange. However, advanced malignancy can produce an almost identical thrombotic microangiopathy (TMA) that responds poorly to plasma exchange, and for which the definitive treatment is control of the underlying cancer. We report a 77-year-old woman with metastatic breast cancer and extensive osseous metastatic disease who presented with nausea, palpitations, generalized weakness, and transient neurological symptoms. Investigations revealed severe anemia, moderate but rapidly progressive thrombocytopenia, markedly elevated lactate dehydrogenase, elevated indirect bilirubin, undetectable haptoglobin, a negative direct antiglobulin test, and schistocytes on the blood smear. Brain magnetic resonance imaging showed acute bilateral frontal ischemic infarctions. Although early coagulopathy and active cancer yielded an intermediate PLASMIC score, TTP could not be excluded. Empiric plasma exchange and high-dose corticosteroids produced no hematological improvement, and the patient died shortly thereafter. ADAMTS13 testing was delayed by a pre-analytical error. The clinical course and lack of response favored malignancy-associated MAHA with disseminated intravascular coagulation over TTP. This case underscores that in patients with disseminated malignancy, MAHA with thrombocytopenia and neurological signs should raise early suspicion of cancer-associated TMA, even while TTP is treated empirically.