Predominant tubulointerstitial nephritis in a patient with systemic lupus nephritis.

In most cases of systemic lupus erythematosus (SLE), glomerular lesions are the main renal complication. Although tubulointerstitial lesions are often associated with severe glomerular lesions, predominant or isolated tubulointerstitial injury in the presence of minimal glomerular abnormalities with SLE, so-called predominant tubulointerstitial lupus nephritis, is rare. Only ten cases are reported in the English literature. Herein, we describe the case of a 64-year-old man with SLE who presented with acute renal deterioration attributable to acute tubulointerstitial nephritis. Renal biopsy showed diffuse infiltration of inflammatory mononuclear cells in the interstitium and tubulitis without significant glomerular lesions. Immunofluorescence study revealed positive staining for IgG, C3, and C1q along the renal tubular basement membrane (TBM). Electron microscopy also showed electron-dense deposits in the TBM. Other causes of tubulointerstitial injury, such as drug use and infection, were ruled out. Taking these findings together with the presence of antitubular basement membrane antibody, predominant tubulointerstitial lupus nephritis was diagnosed. Treatment with oral corticosteroids for 6 weeks improved renal function. Even after tapering of the corticosteroid, renal function and serological markers of SLE activity have remained stable in this patient for more than 12 months.

Acute tubulointerstitial nephritis associated with autoimmune-related pancreatitis.

Various etiologic factors have been identified in tubulointerstitial nephritis (TIN), including allergic drug reaction, infection, and immune-mediated disease. Immune-mediated TIN without significant glomerular involvement has been reported to occur as a renal complication secondary to Sjögren's syndrome, lupus nephritis, and antitubular basement membrane antibody-related disease. We present a first case of acute TIN associated with autoimmune-related pancreatitis (AIP). A 64-year-old man was referred to our division from a surgeon for the close examination of renal dysfunction. The pancreatic and biliary imaging showed segmental narrowing of the pancreatic duct with localized swelling of the pancreatic head, suggesting the carcinoma of the pancreatic head at that time. However, the laboratory findings also showed renal dysfunction with high level of serum immunoglobulin G and hypocomplementemia. Renal biopsy was performed to investigate the etiology of the renal dysfunction. The renal biopsy specimen showed acute TIN. The patient had no drug history, which may cause TIN. Oral corticosteroid therapy improved the renal function as well as histological damage, the pancreatic imaging study, and the laboratory tests of pancreatic and hepatobiliary enzyme. Although the pancreatic biopsy has not performed in our patient, his clinical course confirmed us that AIP was the final diagnosis for his pancreatic lesion. Despite further examination, there was no evidence of other autoimmune-related diseases such as Sjögren's syndrome. To our knowledge, this is the first report of acute TIN associated with AIP. We suggest that AIP may be an etiologic factor in some cases of TIN.