A masquerading mass: an unusual presentation of IgG4-related systemic disease with tubulointerstitial nephritis

IgG4 tubulointerstitial nephritis (IgG4-TIN) is the most common form of IgG4 renal disease. When IgG4-TIN is accompanied by other systemic manifestations the disease is known as IgG4-related systemic disease (IgG4-RSD). IgG4-RSD is well recognised in the form of tubulointerstitial nephritis (IgG4-related TIN) and may present with renal failure by mimicking neoplasms (tumefactive lesions) or with both features.