Idiopathic hypocomplementemic interstitial nephritis with extensive tubulointerstitial deposits

Most forms of interstitial nephritis are cell mediated and lack tubulointer stitial immune deposits. These forms include allergic, infectious, and idio pathic interstitial nephritis. Immune complex deposits in the tubular basem ent membranes and interstitium most commonly are encountered in conjunction with glomerular diseases, Predominantly tubulointerstitial immune deposits without significant glomerular involvement can occur in Sjogren's syndrome and in a small subset of lupus nephritis. We report eight unusual cases of tubulointerstitial nephritis with massive tubulointerstitial immune deposi ts occurring in adults with hypocomplementemia and no evidence of systemic lupus erythematosus or Sjogren's disease. Most patients were older men. The renal biopsy specimens manifested a spectrum of changes ranging from tubul ointerstitial nephritis to atypical lymphoid hyperplasia to changes suggest ive of marginal zone B-cell lymphoma. Chronic local antigenic stimulation m ay predispose to lymphoma in these cases, analogous to what is postulated t o occur in cases of mucosa-associated lymphoid tissue (MALT) lymphomas in e xtranodal sites, such as salivary gland, stomach, end thyroid, The preferen tial tubulointerstitial immune deposition and significant interstitial plas ma cell component suggest pathomechanisms that involve local immune complex formation. (C) 2001 by the National Kidney Foundation, Inc.