CASE PRESENTATION: A 63-year-old Hispanic male with hypertension presented with non-productive cough for two weeks, associated with shortness of breath and fatigue. He was tacchycardic, tacchypneic, saturating 92% on room air, with a temperature of 102.1° Farenheit. Pulmonary exam revealed scattered rhonchi in the right lower lung field and diminished breath sounds in the left base. Laboratory investigations showed leukocytosis. Computed tomography of the chest showed areas of nonspecific groundglass attenuation in the right upper lobe and inferior right middle lobe along with enlarged hilar and subcarinal lymph nodes. IgM titer for Mycoplasma pneumoniae was 5081 units/mL (Ref < 770). Despite treatment with Ceftriaxone and Azithromycin, his hypoxia worsened as he became jaundiced with notable scleral icterus. His hemoglobin level decreased from 13.3 g/dL to 6.6 g/dL. Haptoglobin level was consistently low along with elevations in LDH, total and direct bilirubin. A peripheral blood smear revealed red blood cell agglutination with no evidence of spherocytes. Direct antiglobulin test was 3+ positive for C3d and weakly positive for IgG. Cold-agglutinin antibody titer obtained towards the end of his stay was 1:64, confirming the diagnosis of cold agglutinin autoimmune hemolysis. He finished a 14-day course of Azithromycin, received warmed IV fluids along with strict cold avoidance, leading to an improvement of his symptoms and hemoglobin. Two weeks after discharge, his hemoglobin continued to increase to 12.4g/dL.