Tubulointerstitial nephritis with IgM-positive plasma cells complicated by liver failure

Tubulointerstitial nephritis (TIN) is characterized by inflammation of the renal interstitium with the infiltration of immune cells, mainly consisting of T cells. Recently, patients with TIN with the predominant infiltration of immunoglobulin M (IgM)-positive plasma cells were reported, coined IgMPC-TIN. Here we report the case of a 70-year-old woman diagnosed with Fanconi syndrome and renal tubular acidosis. Renal biopsy revealed IgMPC-TIN. Her renal dysfunction and clinical findings improved after corticosteroid therapy. However, the patient died of progressive liver failure and spontaneous bacterial peritonitis. In laboratory tests, viral hepatitis was excluded, and autoantibodies associated with liver diseases were negative. Generally, IgMPC-TIN is often complicated by primary biliary cholangitis (PBC), whereas her autopsy revealed the local infiltration of IgM-positive plasma cells, obliterative portal venopathy, and nodular regenerative hyperplasia in liver. This case is the first demonstration that IgMPC-TIN is also seen in liver disease with nodular regenerative hyperplasia, although IgMPC-TIN is more common in anti-M2 antibody-positive disease.