No increasing of the number of B cells producing GPIIb/IIIa antibody in the patient peripheral blood with ELISPOT assay and the unbinding of anti-GPIb antibody to the patient's platelets with flow cytometric analysis suggested that autoantibody adhering to GPIb on the platelets was responsible for thrombocytopenia. This evidence concerns the gene ITGA2B and Thrombocytopenia.