Undiagnosed Metastatic Breast Carcinoma Presenting as Thrombotic Thrombocytopenic Purpura.

Cancer-associated thrombotic microangiopathy has a documented relationship with metastatic disease. Other examples of thrombotic microangiopathy (TMA) include thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). All these conditions can present with microangiopathic hemolytic anemia as well as thrombocytopenia. However, when these findings occur in association with cancer, they often carry a poor prognosis. Though associated with metastasis, microangiopathic hemolytic anemia, and thrombocytopenia have rarely been seen as the presenting signs of malignancy. We present the case of a 66-year-old female with no known history of cancer who exhibited an intriguing clinical presentation, including progressive dyspnea worsening with exertion, diarrhea, and dizziness. Laboratory investigations revealed Coombs-negative hemolytic anemia with schistocytes on blood smears and thrombocytopenia. The patient's condition raised concerns for TTP, prompting the initiation of plasmapheresis. However, despite treatment, the anemia and thrombocytopenia showed no improvement, leading to further investigations. Ultimately, a bone marrow biopsy revealed tumor cells arranged in nests and single files, leading to a diagnosis of metastatic carcinoma, consistent with breast primary. This was the patient's first known sign of breast cancer. This case emphasizes the significance of considering metastatic cancer as a potential differential diagnosis in patients presenting with similar signs and symptoms.