Glucocorticoid-Responsive Cold Agglutinin Disease in a Patient with Rheumatoid Arthritis

A 57-year-old man with rheumatoid arthritis developed severe anemia during treatment with adalimumab plus methotrexate. Cold agglutinin disease was diagnosed because haptoglobin was undetectable, cold agglutinin was positive (1 : 2048), and the direct Coombs test was positive (only to complement). Although the cold agglutinin titer was normalized (1 : 64) after treatment with prednisolone (0.7 mg/kg/day for two weeks), the patient's hemoglobin did not increase above 8 g/dL. When cold agglutinins were reexamined using red blood cells suspended in bovine serum albumin, the titer was still positive at 1 : 1024. Furthermore, the cold agglutinin had a wide thermal amplitude, since the titer was 1 : 16 at 30°C and 1 : 1 at 37°C. This suggested that the cold agglutinin would show pathogenicity even at body temperature. After the dose of prednisolone was increased to 1 mg/kg/day, the patient's hemoglobin rapidly returned to the normal range. The thermal amplitude test using red blood cells suspended in bovine serum albumin is more sensitive than the standard test for detecting pathogenic cold agglutinins.