IgG-related disease: an atypical presentation of steroid-responsive renal mass.

IgG-related disease (IgG-RD) is a systemic fibroinflammatory disease characterised by dense lymphoplasmacytic infiltration rich in IgG-positive plasma cells, storiform fibrosis and obliterative phlebitis. Serum IgG levels are typically elevated but half of the patients had normal serum IgG levels. IgG-RD represents a spectrum of diseases that involve various organs such as the pancreas, liver, kidneys, and salivary glands often manifesting as diffuse organ enlargement or a mass-like lesion mimicking cancer.