This patient was a 70-year-old woman, diagnosed with high-grade myelodysplastic syndrome. After having achieved remission with systemic chemotherapy, she underwent a haploidentical stem cell transplantation. For GvHD prevention, she received post-transplant cyclophosphamide, tacrolimus, and mycophenolate mofetil. CMV serostatus: D−, R+. Despite anti-CMV prophylaxis with letermovir, CMV viral load increased from month 3 on, and a preemptive treatment with valganciclovir was introduced. Given a further increment of the viral load despite this treatment, foscarnet was subsequently started. Phosphonoformate crystalluria (proven by infrared spectrometry) was observed at day 9 after onset of foscarnet associated with a nonglomerular hematuria and renal tubular epithelial cells in urine sediment. The patient developed AKI KDIGO stage 1 at day 14.
A 59-year-old woman diagnosed with acute myeloid leukemia received successfully an allogeneic hematopoietic stem cell transplantation from an HLA-compatible unrelated donor following a reduced-intensity conditioning. The GvHD prophylaxis regimen was mycophenolate mofetil and cyclosporine. In the post-transplantation phase, the patient presented several complications, such as reactivation of CMV disease (CMV serostatus: D+, R+). Foscarnet was initiated and phosphonoformate crystalluria (proven by infrared spectrometry) was observed 7 days after onset of therapy associated with renal tubular epithelial cells in urine sediment. No hematuria was observed. The patient developed AKI KDIGO stage 1 24 days after foscarnet initiation.