#370 Macroscopic hematuria-associated severe acute kidney injury from thin basement membrane disease

Abstract

Abstract Background Macroscopic hematuria-associated acute kidney injury (MH-AKI) is a rare condition reported in IgA nephropathy and others, and the mechanism of renal tubular damage caused by red blood cells in the tubules appears to be similar to that of anticoagulant nephropathy. Case presentation A 66-year-old Japanese woman with no previous medical history was referred to our hospital with anuric severe kidney injury. Seven days earlier, she had transient acute lumbar back pain, which was followed by gradual worsening of malaise and loss of appetite. On admission, her serum BUN was 147.8 mg/dL, serum Cr 18.57 mg/dL, hemoglobin 11.2 g/dL, urinary red blood cells> 100/HPF, urinary protein 28.8 g/gCr, no hydronephrosis in either kidney, but a small stone in the right kidney. After admission, while starting hemodialysis, she was treated with methylprednisone 1000 mg for 3 days followed by prednisone 40 mg/day because of suspected rapidly progressive glomerulonephritis, but both MPO-/PR3-ANCA and anti-GBM antibodies were negative. Renal biopsy from left kidney showed acute tubular injury with large amounts of red blood cells and red blood cell casts filling the distal tubules (Figure), and prednisone was discontinued. Subsequently, urine flowed out with gross hematuria, and her hematuria and renal function improved with increased urine output, and she was weaned from hemodialysis. Electron microscopy showed glomerular thin basement membrane (TBMD) (Figure). Her renal function and hematuria slowly improved and the right kidney stone disappeared. Microscopic hematuria eventually disappeared, and her serum Cr level was 1.1 mg/dL one year after onset. Conclusions This is the first report of MH-AKI in TBMD without a background of anticoagulation, severe thrombocytopaenia, or iron overload. In one report, compared to IgA nephropathy, TBMD is associated with increased urinary Ca and uric acid excretion, which is associated with gross hematuria and back pain [1]. In this case of MH-AKI from TBMD, both red blood cells and crystal formation in the tubular lumens may have transiently and synergistically caused renal tubular obstruction and heme iron-induced tubular damage.