[Multiple microthromboses with autoimmune hemolytic anemia after BNT162b2 mRNA vaccination].

A 68-year-old man was referred to our hospital with dizziness and mild fever one week after receiving the second dose of the COVID-19 mRNA vaccine (BNT162b2). Laboratory tests showed hemolytic anemia and a positive direct Coombs test, and he was diagnosed with autoimmune hemolytic anemia (AIHA). On admission, the patient had impaired consciousness with auditory hallucinations, and a head MRI scan showed multiple high-signal areas on diffusion-weighted imaging, suggesting multiple recent infarctions. Echocardiography also showed decreased wall motion in the inferior and posterior walls. A skin biopsy to investigate the cause revealed many platelets and fibrin thrombi in the capillaries and small veins, which was considered the cause of the organ damage. After starting prednisolone (1 mg/kg) for AIHA, hemolytic anemia as well as impaired consciousness, and decreased wall motion rapidly improved. Microthrombosis after BNT162b2 mRNA vaccination is rare, and autoimmune abnormalities appeared to contribute to onset in this case.