A case of an ABO-incompatible renal transplant with abundant intratubular basement membrane immune deposits.

We present a case of a 30-year-old man who received an ABO-incompatible renal transplant from his mother in 1996 after haemodialysis for 3 years. Although his renal function was stable, a renal biopsy was performed while he was in hospital for treatment of herpes zoster in 1999. Light microscopy provided no evidence of obvious acute or chronic rejection but a double contour pattern was observed in many tubular basement membranes (TBM). Immunofluorescence microscopy revealed deposits of IgG and C3 on the TBM in the absence of glomerular deposition. Massive electron-dense deposits were observed clearly by electron microscopy within TBM, revealing splitting and lamellation. This implies that the deposits resulted from the formation of immune complexes, but not from anti-TBM antibody. Although the role of TBM deposits in tubular injury is controversial, careful observation of patients with such deposits may be required because of their potential ability to induce immune reactions.