Hemolytic Anemia in the Setting of Atypical Pneumonia: A Case of Cold Agglutinin Disease.

Cold agglutinin hemolytic anemia (cAHA) is a rare autoimmune disorder characterized by the production of cold agglutinins. We present a case of secondary cAHA in a 23-year-old female with severe anemia and unexplained hemolysis. The patient exhibited findings indicative of hemolysis and a positive direct antiglobulin test (DAT) with complement alone. Additional investigations revealed incidental lung infiltrates, negative serology for infections and autoimmune diseases, and a low cold agglutinin titer. The patient showed a favorable response to doxycycline and supportive therapy, including multiple packed red blood cell transfusions. At the two-week follow-up, the patient had a stable hemoglobin level with no evidence of ongoing hemolysis. This case highlights the importance of considering secondary cAHA in patients with cold symptoms or unexplained hemolysis. Primary cAHA patients may require more aggressive treatment, including rituximab and sutilumab.