Clinicopathologic Characterization of IgG4-Rich Pediatric Head and Neck Lesions

center dot Context.-Immunoglobulin G4 (IgG4)-related disease is rare but well characterized in adults; however, the clinical and histologic manifestations in children may differ. Objective.-To review the clinical and histologic features of IgG4-rich head and neck lesions in a pediatric population. Design.-Retrospective search for cases with IgG4 immunohistochemical staining performed at our institution from 2011 to 2019. Review of clinical courses, serology profiles, histologic patterns, and immunohistochemical staining patterns. Results.-Four pediatric IgG4-rich lesions were identified and showed distinct histologic patterns from adult IgG4-related disease, including absence of pathognomonic findings associated with the latter. One case showed intralesional immunoglobulin light-chain restriction. Clinical review showed serum IgG4 elevation in 2 of 4 cases, presence of additional autoantibody positivity, and a generally benign/treatment-responsive clinical course . Conclusions.-Pediatric IgG4-related disease shows distinct clinical, serologic, and histologic features from its adult counterpart. Pediatric IgG4-related disease involving the orbit has unique clinical characteristics, including frequently normal serum IgG4 levels and female predominance. Awareness of and evaluation for these features may improve diagnosis and treatment. (Arch Pathol Lab Med. 2022;146:611-618; doi: 10.5858/ arpa.2021-0041-OA)