IgG4-related tubulointerstitial nephritis with eosinophilia

Kidney biopsy from a 45-year-old male patient with a history of type 1 (IgG4-related) autoimmune pancreatitis. The patient presented with a serum creatinine of 2.5 mg/dL. A glomerulus is evident in this biopsy, but the inflammatory infiltrate is concentrated in the region of the tubules and interstitium. There is a lymphoplasmacytic infiltrate accompanied by fibrosis and ample numbers of eosinophils.