Irreversible glomerular lesions induced by crystal precipitation in a renal transplant after foscarnet therapy for cytomegalovirus infection

Aims: Foscarnet is an antiviral agent used to treat cytomegalovirus infecti on in AIDS patients and in transplant recipients. In most cases, foscarnet induces reversible tubulo-interstitial lesions which can be avoided by corr ect hydration. We report the first case of crystal foscarnet precipitation within glomerular capillaries in a renal transplant. Methods and results: The recipient, a 49-year-old man, developed a nephroti c syndrome with haematuria and an acute renal failure after foscarnet thera py for cytomegalovirus (CMV) infection. The polarization examination of the first graft biopsy revealed the presence of birefringent crystals within g lomeruli and tubules. Infrared analysis attested to the presence of trisodi um foscarnet salts and mixed sodium calcium salts coloured by Von Kossa's r eaction, A second biopsy showed glomerular sclerosis, interstitial fibrosis , tubular atrophy and crystal vanishing. Polymerase chain reaction (PCR) in situ applied to this biopsy confirmed the diagnosis of cytomegalovirus inf ection. Conclusions: These adverse effects might be the result of a toxic synergy b etween foscarnet and other drugs. In cases with crystalline precipitation, graft biopsy remains the best mean of diagnosis and follow-up of glomerular damage.