Paraneoplastic Evans Syndrome in a Patient With Prostate Cancer With Small Cell Transformation

Paraneoplastic syndromes are defined as tumor‐associated indirect systemic effects. Prostate cancer-associated paraneoplastic syndromes typically have endocrine, neurologic, and dermatologic manifestations. Reports have suggested up to 70% of metastatic prostate cancers manifest as paraneoplastic entities. Although common in hematological malignancies, it is rare for prostate cancer and other solid tumors to be associated with immune-mediated cytopenias such as Evans syndrome. Based on our PubMed search for the keywords Evans syndrome and prostate cancer, only one other case has been reported in the literature with this association. We report the second such case in a 63-year-old male who initially presented with hemolytic anemia and thrombocytopenia. He was diagnosed with Evans syndrome with initial responses to both steroids and intravenous immunoglobulin. Extensive workup, including an eventual bone marrow biopsy, revealed metastatic prostate cancer with transformation to small cell neuroendocrine carcinoma.