Foscarnet-induced crystalline glomerulonephritis with nephrotic syndrome and acute renal failure after kidney transplantation

associated with acute tubulointerstitial nephritis. Crystals in glomerular capillary lumens have also been observed in patients with acquired immunode ficiency syndrome who were treated with foscarnet for cytomegalovirus disea se. We describe a kidney transplant recipient who developed a nephrotic syn drome with microscopic hematuria and nonoliguric acute renal failure within 15 days after starting foscarnet therapy for cytomegalovirus infection. A kidney biopsy specimen showed the presence of crystals in all glomeruli and in proximal tubules. Fourier transform infrared microscopy analysis demons trated that crystals were made from several forms of foscarnet salts: mixed calcium and sodium salts, and unchanged trisodium foscarnet salts. Renal f unction and proteinuria spontaneously improved, and a second transplant bio psy performed 8 months after the first one revealed fibrotic organization o f half of the glomeruli and of interstitial tissue, and crystal vanishing, me were thus able to provide proof of the possible precipitation of foscarn et in a transplanted kidney.