A 71-year-old woman diagnosed with acute myeloid leukemia underwent, while in complete remission, a nonmyeloablative allogeneic hematopoietic stem cell transplantation with HLA-compatible unrelated donor. Conditioning regimen consisted in fludarabine and total body irradiation; graft-versus-host disease (GvHD) prophylaxis consisted of mycophenolate mofetil and ciclosporine. Following transplantation, the patient presented multiple complications such as a reactivation of CMV disease (CMV serostatus: D−, R+). Ganciclovir was administered without effect on the viral load of CMV. Hence, based on in vitro documentation of resistance of CMV to ganciclovir, the patient was switched to foscarnet. Phosphonoformate crystalluria (proven by infrared spectrometry) was observed 14 days after the onset of foscarnet therapy and associated with a nonglomerular hematuria and renal tubular epithelial cells in urine sediment. Progressive elevation of serum creatinine concentration occurred (AKI Kidney Disease: Improving Global Outcomes [KDIGO] stage 3), despite adaptation of foscarnet doses to kidney function. The patient died after probable fungal bronchopneumonia and septicemia while still on foscarnet.
A 35-year-old man diagnosed with acute lymphoblastic leukemia achieved a second complete remission following salvage chemotherapy after a first relapse. Stem cell transplantation from an HLA-matched unrelated donor was performed following myeloablative conditioning. CMV serostatus was D−, R−. To prevent GvHD, cyclosporine with a short course of methotrexate was administered. Numerous complications occurred after transplantation, including an human herpesvirus 6 encephalitis. For the latter, ganciclovir was started and replaced after 24 hours by foscarnet because of concerns about known associated myelotoxicity with high doses of ganciclovir. Phosphonoformate crystalluria (proven by infrared spectrometry) was observed 7 days after onset of foscarnet associated with a nonglomerular hematuria but without renal tubular epithelial cells in urine sediment. Because of a stable kidney function, foscarnet administration was maintained at unchanged doses. Despite the human herpesvirus 6 encephalitis resolution, the patient died from acute respiratory failure due to uncontrolled bleeding.