Orbital imaging features and nerve ultrasound photographs. Left optic nerve and orbital muscle can be detected in the lesion in axial (A) and coronal (B) imaging. (arrow). Marked infiltration of IgG4‐positive plasma cells is shown (C). Nerve segmental enlargement was shown of right peroneal nerve bundle (arrow) (D) and left peroneal nerve bundle(arrow) (E). A perineural IgG4‐positive plasma cell infiltration was not observed (F) (original magnification ×200)