[Hypocomplementemic tubulointerstitial nephritis in IgG4-related disease].

A novel lymphoproliferative disorder producing plasma cell expansion in the affected organ with fibrotic or sclerosing changes, known as ''IgG4-related disease'', was defined in Japan by Umehara's group in 2010. We present the first case reported in Italy. In 2007, a 63-year-old man presented with epigastric pain and elevated serum lipase levels. Computed tomography of the abdomen revealed a Kuttner's tumor of the pancreas. The patient underwent a biliary-enteric anastomosis, and biopsy of the pancreas revealed massive infiltration of lymphocytes and plasma cells. The patient was diagnosed with chronic sclerosing pancreatitis. After one year, he began to show signs of sicca syndrome and at the same time developed progressive renal failure. Immunological tests revealed hypocomplementemia, and the renal biopsy specimen showed diffuse interstitial inflammation. The infiltrate was composed of lymphocytes, while infiltrating plasma cells showed immunoreactivity to IgG-4. Sialography using a radioisotope revealed severe involvement of the salivary glands, and Schirmer's test gave a positive result. This led us to diagnose hypocomplementemic tubulointerstitial nephritis in IgG4-related disease. Corticosteroid treatment resulted in rapid improvement including disappearance of the sicca syndrome and progressive amelioration of renal function. After six months, we discontinued steroid administration and started mycophenolate mofetil to maintain a low degree of immunosuppression. Follow-up after two years showed that this therapy continued to be quite effective in our patient.