Acute kidney injury due to thin basement membrane disease mimicking Deferasirox nephrotoxicity: a case report

Macroscopic hematuria-associated severe acute kidney injury triggered by kidney stone formation in a patient with thin basement membrane and no history of microscopic hematuria

Macroscopic hematuria (MH)-associated acute kidney injury (AKI) is a rare condition that causes acute tubular damage due to severe glomerular bleeding with MH. A 66-year-old Japanese woman with no significant past medical history was referred for severe kidney injury with oliguric MH. Her prior medical checkup results showed no occult blood in her urine. Seven days earlier, she had experienced transient severe acute right lumbar back pain. On admission, her serum urea nitrogen was 147 mg/dL, serum creatinine (sCr) 18.3 mg/dL, urinary red blood cells (RBCs) > 100/hpf, urinary protein 28.8 g/gCr, with no hydronephrosis in either kidney, but two stones were found in the right kidney and right ureteropelvic junction. At the start of her hemodialysis, the patient was treated with high-dose steroids because of suspected rapidly progressive glomerulonephritis. A renal biopsy of the left kidney showed acute tubular injury with massive RBC casts filling the tubular lumen. Glomerulitis was not detected, but electron microscopy revealed diffuse glomerular thin basement membrane (TBM). Despite immediate steroid discontinuation, the patient's renal function and MH improved, and she was weaned from hemodialysis. The stones resolved 2 months after onset, but microscopic hematuria persisted for 7 months post-onset. The sCr level was fixed at 1.1 mg/dL 20 months post-onset. This is the first report of MH-AKI in a TBM without the risk of MH-AKI development, such as bleeding tendency or iron overload. In this TBM, a colic attack of the renal urinary tract induced glomerular bleeding, and intolerance to hematuria may have caused severe tubular damage.

Evidence for the Metabolic Activation of Deferasirox In Vitro and In Vivo

Deferasirox (DFS) is used for the treatment of iron accumulation caused by the need for long-term blood transfusions, such as thalassemia or other rare anemia. Liver injury due to exposure to DFS has been documented, and the toxic mechanisms of DFS are unknown. The present study aimed to investigate the reactive metabolites of DFS in vitro and in vivo to help us understand the mechanisms of DFS hepatotoxicity. Two hydroxylated metabolites (5-OH and 5'-OH) were identified during incubation of DFS-supplemented rat liver microsomes. Such microsomal incubations fortified with glutathione (GSH) or N-acetylcysteine (NAC) as capture agents offered two GSH conjugates and two NAC conjugates. These GSH conjugates and NAC conjugates were also detected in bile and urine of rats given DFS. CYP1A2 and CYP3A4 were found to dominate the metabolic activation of DFS. Administration of DFS induced decreased cell survival in cultured primary hepatocytes. Pretreatment with ketoconazole and 1-aminobenzotrizole made hepatocytes less susceptible to the cytotoxicity of DFS.