IgG4-related disease: The utility of (18)F-FDG PET/CT in diagnosis and treatment.

Objective: IgG4-related disease (IgG4-RD) is a systemic mass-forming fibro-inflammatory condition which can affect nearly every organ system. Its pathophysiology remains incompletely understood, but affected tissues are characterized by a lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells which cause chronic inflammation, storiform fibrosis and phlebitis. These findings on histopathological specimens are considered the gold standard for the diagnosis.