[IgG4-related kidney disease. Diagnosis and treatment].

IgG4-related disease (IgG4-RD) is a systemic inflammatory disorder that can affect most organs/tissues like sarcoidosis. The kidney is one of the most frequently affected organs. While tubulointerstitial nephritis (TIN) with characteristic imaging findings is the representative lesion of IgG4-related kidney disease (IgG4-RKD), a variety of glomerular lesions, particularly membranous nephropathy, sometimes overlap on TIN. Clinically, either decreased renal function and/or characteristic imaging findings such as multiple low-density lesions on contrast-enhanced computed tomography are typical presenting features. Histologically, plasma cell (PC)-rich TIN accompanied by characteristic fibrosis called storiform fibrosis with dense IgG4-positive PC infiltration is a typical finding. Although a swift response to corticosteroid is a very important feature of IgG4-RKD, in cases with moderately to severely decreased renal function before therapy, only partial recovery of renal function is obtained. This review provides a comprehensive overview of IgG4-RKD from the clinical, laboratory, imaging, and histological aspects and also addresses some of the therapeutic issues concerning it.