Warm Autoimmune Hemolytic Anemia Unmasked by Blood Transfusion in a Patient With Prostate Cancer: A Case Report

We report the case of a 65-year-old man with non-metastatic prostate cancer who presented with symptomatic anemia (Hb 66 g/L). With no bleeding source and normal iron studies, anemia of chronic disease was initially suspected. Following transfusion of one unit of red blood cells, he developed clinical and biochemical features of hemolysis. The direct antiglobulin test (DAT) was strongly positive (IgG +4, C3 +3), confirming warm autoimmune hemolytic anemia (AIHA). Further transfusions were administered under steroid cover. Autoimmune serology revealed positive antinuclear antibodies (ANA) and markedly elevated dsDNA by enzyme-linked immunoassay (ELISA) but negative <i>Crithidia</i> assay, indicating low-affinity antibodies and no clinical features suggestive of systemic lupus erythematosus (SLE). No monoclonal proteins were detected, and immunoglobulin profile showed polyclonal hypergammaglobulinemia. The patient had no features to suggest lymphoproliferative disorders. He responded to high-dose prednisolone and supportive treatment without further transfusions. While warm AIHA is more frequently reported in association with chronic lymphocytic leukemia (CLL) or SLE, its occurrence in patients with solid organ malignancies such as prostate cancer is rare. Given the absence of systemic autoimmune disease and drug exposure, and in the context of known non-metastatic prostate cancer, this case of warm AIHA is best explained by malignancy-associated immune dysregulation.