Abstract
This is a case report of a patient who developed severe acute kidney disease with kidney biopsy showing interstitial nephritis, plasma cell infiltration and immunoglobulin G4 (IgG4) expression consistent with IgG4-related kidney disease. There were no other systemic features of IgG4-related disease. The patient was treated with corticosteroids and mycophenolate. This case highlights the need to consider IgG4-related kidney disease even in the absence of other systemic features. Isolated renal involvement is underrecognized and can lead to missed diagnosis. It also illustrates that mycophenolate can be used as a steroid sparing agent in this condition; an observation that adds to the limited literature in this field.