Pediatric orbital IgG4-related disease: A case series.

Purpose: Immunoglobulin G4 (IgG4)-related orbital disease is an uncommon fibroinflammatory condition characterized by IgG4-positive plasma cell infiltration of orbital structures. While its features are well-recognized in adults, pediatric cases remain exceedingly rare, with limited reports in the literature. Observations: We describe three pediatric female patients with IgG4-related orbital disease, aged 5, 11, and 16 years, who presented with progressive proptosis and globe displacement. Orbital imaging in all cases demonstrated infiltrative lesions involving the lacrimal gland. Histopathologic confirmation was obtained in each, showing dense lymphoplasmacytic infiltrates with cluster of differentiation 138 (CD138) positivity and a high proportion of IgG4-positive plasma cells. Treatment primarily consisted of systemic corticosteroids and immunomodulatory therapy. Rituximab was successfully administered in one refractory case, leading to substantial clinical improvement. Conclusions and importance: Pediatric IgG4-related orbital disease, although rare, should be considered in the differential diagnosis of orbital masses in children, particularly when the lacrimal gland is involved. Histopathology remains essential for diagnosis, and systemic corticosteroids constitute the mainstay of therapy, with immunosuppressants and biologics reserved for refractory disease.