The clinical picture of a febrile illness with persistent dry cough, increasing dyspnea, progressive anemia, mainly indirect hyperbilirubinemia, interstitial infiltrate on chest x-ray and a history of furnace cleaning a few weeks prior to the onset of symptoms raises the possibility of an interstitial pneumonia. Mycoplasma or Legionella are the main suspects, with Mycoplasma taking the lead because the progressive anemia with indirect hyperbilirubinemia suggests that a hemolytic process is occurring. Cold agglutinins and mycoplasma serology were requested, and the cold agglutinins came back strongly positive with a titre of 1:2,048. Direct antiglobulin test (DAT)-IgG was negative but DAT-CD3 was weakly positive.

Matthew was started on intravenous erythromycin and steroids. Within 48 hours, his symptoms improved and hemoglobin stabilized. He was discharged home 5 days later on oral erythromycin for another 5 days and tapering doses of steroids. Six weeks later, his hemoglobin is back at 142 g/L and his cold agglutinin is 1:30. The weather might have worsened the hemolysis as the cold agglutinins are more likely to precipitate and cause hemolysis at colder temperatures. Mycoplasma IgG antibody is now found to be positive; hepatitis serology is negative. Final diagnosis: cold agglutinin-induced hemolytic anemia, likely secondary to Mycoplasma interstitial pneumonia.