C4d-expressing glomerulopathy and proteinuria post transplantation of a too-big-for-size mismatched kidney allograft: An unusual case with good outcome .

A 5-year-old severely growth-retarded child with tubulointerstitial, oliguric end-stage renal disease received an adult-size kidney transplant. Three years post grafting under standard triple immunosuppression (mycophenolate mofetil, tacrolimus, and prednisone) de novo nephrotic range proteinuria without the nephrotic syndrome developed. Graft function was normal (serum creatinine: 0.2 - 0.3 mg/dL), there were no donor-specific HLA antibodies (DSA), and the urine sediment was inactive. Two biopsies collected 3 and 4 years post-transplantation showed severe glomerular capillary wall remodeling and associated pseudolinear C4d staining as morphologic correlates for the proteinuria. Changes resembled those seen in so-called "size-mismatch transplant glomerulopathies". There was no evidence of a glomerulonephritis, acute or chronic rejection including transplant glomerulopathy, interstitial fibrosis, peritubular capillary C4d deposits, or multilamination of peritubular capillary basement membranes. The glomerular changes were not detected in the implantation zero-hour biopsy or the recipient's native renal biopsy. At the end of follow-up 64 months post transplantation, proteinuria persisted at subnephrotic levels in the setting of stable graft function and undetectable DSAs. This unique case adds to the list of causes of nonrejection-associated post-transplant proteinuria. It demonstrates for the first time that a too-large-for-body-size mismatched graft is associated with a presumably sheer stress-induced C4d expressing glomerulopathy, severe proteinuria, and favorable outcome.
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