A Rare Case of Cold Agglutinin Syndrome Associated With Legionella Pneumonia.

Cold agglutinin syndrome (CAS) is a rare subset of autoimmune hemolytic anemia (AIHA) and can be classified as either primary or secondary. Secondary cold agglutinin disease has been associated with both viral and bacterial pathogens with the most common bacterial pathogen being Mycoplasma pneumoniae. Legionella pneumonia is a well-known causative agent for community-acquired pneumonia that can lead to a severe disease requiring hospitalization that is rarely associated with AIHA. We highlight the importance of recognizing Legionella pneumonia as a causative pathogen for CAS.