Interstitial nephritis and high titers of PR3-ANCA: an unusual manifestation of ANCA-associated disease

We present the case of a 75-year-old female with weight loss, anemia, systemic signs of inflammation, mild renal insufficiency, microscopic hematuria, mixed glomerular and tubular proteinuria, and high titers of PR3-ANCA. Renal biopsy demonstrated interstitial nephritis with some sclerosed but otherwise normal glomeruli. Extensive work-up showed no signs of granulomatous inflammation or other vasculitic organ involvement. We presumed this to be a rare renal manifestation of ANCA-associated disease with the presence of sclerosed glomeruli suggesting a previous history of glomerular involvement. In view of the absence of active vasculitic or granulomatous disease, treatment was limited to low-dose corticosteroids with good response.