[Successful management of cold agglutinin syndrome developing subsequent to rheumatoid arthritis with immunosuppressive therapy].

A 58-year-old man was admitted with shortness of breath in September 2019. He had a severe hemolytic anemia with a high cold agglutinin (CA) titer. He also had arthralgia and finger deformation. He was diagnosed with cold agglutinin syndrome (CAS) secondary to rheumatoid arthritis (RA) based on the clinical course. Occasionally, CAS has been reported to occur in parallel with collagen disease, infectious disease, or malignant tumor. CAS developing secondary to collagen disease occurs less frequently than that to infectious disease or malignant tumors. Furthermore, CAS caused by RA is very rare, even among patients with collagen diseases. Our patient was effectively treated with immunosuppressive therapy including abatacept, which attenuated the symptoms of CAS and RA.