Warm Autoimmune Hemolytic Anemia with a Direct Antiglobulin Test Positive for C3 and Negative for IgG: A Case Study and Analytical Literature Review of Incidence and Severity

Polygenic IgG autoantibodies are implicated in majority of the cases of warm autoimmune hemolytic anemia (WAIHA). In some of these cases, complement (C3) proteins accompany the IgG antibodies. WAIHA mediated by C3 alone is relatively rare. We present an interesting case of WAIHA with a direct antiglobulin test (DAT) positive for C3 but negative for IgG in a 79-year-old woman and perform an analytical literature review of the incidence and severity of this clinical entity.