Tubulointerstitial nephritis with IgM-positive plasmacytoid large lymphocyte infiltration in a patient with primary biliary cirrhosis and Sjögren's syndrome

We report a 38-year-old woman diagnosed with tubulointerstitial nephritis (TIN) on renal biopsy, followed by being diagnosed with primary biliary cirrhosis (PBC) and Sjögren's syndrome (SS). Immunohistochemically, the cellular infiltrates in TIN were mainly composed of small lymphocytes and IgM-positive plasmacytoid large lymphocytes. IgM-positive plasmacytoid large lymphocytes were not identical with, but colocalized with CD3- or CD20-positive lymphocytes. TIN in patients with PBC is very rare and little is known about immunohistochemical characteristics of infiltrating cells in this setting. To our knowledge, this is the first report demonstrating predominant infiltrating of IgM-positive plasmacytoid large lymphocytes in TIN due to PBC and SS.