Tubulointerstitial Nephritis with IgM-positive Plasma Cells Requiring Temporary Hemodialysis.

A 63-year-old Japanese woman was diagnosed with severe kidney dysfunction that required hemodialysis. Testing revealed an elevated serum IgM level (2,650 mg/dL). A kidney biopsy revealed tubulointerstitial nephritis with the infiltration of IgM and CD138 positive cells into the tubulointerstitium. The patient was diagnosed with tubulointerstitial nephritis with IgM-positive plasma cells (IgMPC-TIN) and required hemodialysis. Subsequently, the patient was treated with prednisolone, which improved her kidney function and led to the discontinuation of hemodialysis. Patients with IgMPC-TIN may experience a marked decline in kidney function; however, corticosteroid treatment can improve the outcomes in patients with severe kidney dysfunction.