CD19 and autoimmune thrombocytopenic purpura: Our results revealed the discrepancy in the peripheral of CD19+ B cell percentages was consistent with the autoantibody‐mediated ﻿immunopathology in CTD‐ITP, but failed to show the significant differences in total antiplatelet antibodies, antiphospholipid antibodies, autoantibody profiles, complement 3, complement 4, and four types of immunoglobulins in corticosteroid‐resistant and corticosteroid‐sensitive CTD‐ITP.