[IgG4-related kidney disease: what the nephrologist needs to know]

IgG4 related disease is a systemic fibro-inflammatory disorder characterized by multiple organ and multiple tissue lesions. The real pathogenesis is currentlyactually unknown. For these reasons many authors compare IgG4 related disease to sarcoidosis. Lesions are often localized in the pancreas, salivary and lacrimal glands, biliary ducts, retroperitoneum and in many other organs. The diagnosisis difficult because of mild symptoms and the possibility of mimicking other severe diseases. Therefore, histopathology together with clinical and radiological typical findings are mandatory tools for diagnosis. Steroidtherapy usually enables disappearance of tumor like lesions and complete recovery. Kidney has an extensive organ involvement in the contextof IgG4-related disease. Historically, tubule - interstitial nephritis(TIN) is considered the main renal feature of renal lesions, however recent studies extend the spectrum of renal lesions also to glomerular tuft. These findings allow to introduce in the nosography the term of IgG4related kidney disease (IgG4 RKD). This review focuses on renal involvement in IgG4related disease, in order to help nephrologists to improve their clinical, diagnostic and therapeutic approach to this emerging pleiotropic clinical pattern.