Autoimmune haemolytic anaemia caused by anti-M antibody in a patient with Kawasaki disease.

Intravenous immunoglobulin (IVIG) is a standard therapy for Kawasaki disease (KD), because it prevents formation of coronary artery aneurysm, a major complication of KD. Herein, we report a 3-year-old boy with KD complicated by haemolytic anaemia (HA) which developed following two courses of IVIG. Although both direct and indirect antiglobulin tests and anti-M antibodies were positive in his blood obtained after the onset of HA, indirect antiglobulin tests and anti-M antibodies were negative either in the blood sample before the treatment or the same lot of IVIG products as those used for the therapy, suggesting autoimmune mechanism. This is, to our knowledge, the first report of autoimmune HA caused by anti-M autoantibodies after IVIG therapy in KD.