Cold Agglutinin-Mediated Hemolysis as an Extrapulmonary Manifestation of Mycoplasma pneumoniae Infection: A Case Report.

Mycoplasma pneumoniae (M. pneumoniae) is a frequent cause of community-acquired pneumonia (CAP) in young adults and may present with extrapulmonary manifestations, including hematologic complications such as cold agglutinin-mediated hemolysis. We report the case of a previously healthy 20-year-old Caucasian man who presented with a four-day history of fever, asthenia, anorexia, and dry cough. Imaging revealed extensive left-sided pulmonary consolidation, and empirical therapy for CAP was initiated. During hospitalization, new-onset anemia with erythrocyte agglutination following blood warming raised suspicion of immune-mediated hemolysis, later supported by positive cold agglutinins and serologic confirmation of M. pneumoniae infection. The patient showed progressive clinical and analytical improvement with targeted azithromycin therapy. He remained asymptomatic and hematologically stable at the three-month follow-up. This case reinforces the importance of recognizing significant hematologic manifestations that may accompany or even precede respiratory involvement in M. pneumoniae infections. Early identification of cold agglutinin-associated hemolysis can expedite diagnostic evaluation and guide appropriate therapy, contributing to favorable outcomes.