[Low titer cold agglutinin disease due to anti-HI antibody and a review of this disease in Japan].

A 79 year-old Japanese man was admitted because of brownish urine and Raynaud phenomenon. Laboratory data showed mild anemia with reticulocytosis, positive direct Coombs test against anti-C3, elevated level of lactate dehydrogenase, undetectable level of serum haptoglobin and low titer of cold agglutinin (1:256 at 4 degrees C), the immunoglobulin subclass of which was IgM. Cold agglutinin disease is usually associated with very high levels of cold agglutinins, the specificity of which is anti-I. This case had low titer cold agglutinin disease due to anti-HI cold agglutinin.