Beneficial effect of rituximab in the treatment of recurrent idiopathic membranous nephropathy after kidney transplantation.

BACKGROUND AND OBJECTIVES: Recurrence of the original kidney disease after renal transplantation is an increasingly recognized cause of allograft loss. Idiopathic membranous nephropathy (iMN) is a common cause of proteinuria that may progress to ESRD. It is known that iMN may recur after kidney transplantation, causing proteinuria, allograft dysfunction, and allograft loss. Limited data regarding the frequency and treatment of recurrent iMN are available. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In this single-center study, all patients who had iMN and were receiving a first kidney transplant were included. We retrospectively assessed the incidence of biopsy-confirmed recurrent iMN and compared clinical characteristics of patients with and without recurrence. In addition, the effect of treatment with rituximab on proteinuria and renal allograft function in patients with recurrent iMN was examined RESULTS: The incidence of recurrent iMN was 44%, and recurrences occurred at a median time of 13.6 months after transplantation. Two patterns of recurrence were identified: Early and late. No predictors of recurrence or disease progression could be identified. Treatment with rituximab was effective in four of four patients in stabilizing or reducing proteinuria and stabilizing renal function. CONCLUSIONS: Recurrence of iMN is common even in the era of modern immunosuppression. Rituximab seems to be a valuable treatment option for these patients, although lager studies are needed to confirm our data.

Development of focal segmental glomerulosclerosis after anabolic steroid abuse.

Anabolic steroid abuse adversely affects the endocrine system, blood lipids, and the liver, but renal injury has not been described. We identified an association of focal segmental glomerulosclerosis (FSGS) and proteinuria in a cohort of 10 bodybuilders (six white and four Hispanic; mean body mass index 34.7) after long-term abuse of anabolic steroids. The clinical presentation included proteinuria (mean 10.1 g/d; range 1.3 to 26.3 g/d) and renal insufficiency (mean serum creatinine 3.0 mg/dl; range 1.3 to 7.8 mg/dl); three (30%) patients presented with nephrotic syndrome. Renal biopsy revealed FSGS in nine patients, four of whom also had glomerulomegaly, and glomerulomegaly alone in one patient. Three biopsies revealed collapsing lesions of FSGS, four had perihilar lesions, and seven showed > or =40% tubular atrophy and interstitial fibrosis. Among eight patients with mean follow-up of 2.2 yr, one progressed to ESRD, the other seven received renin-angiotensin system blockade, and one also received corticosteroids. All seven patients discontinued anabolic steroids, leading to weight loss, stabilization or improvement in serum creatinine, and a reduction in proteinuria. One patient resumed anabolic steroid abuse and suffered relapse of proteinuria and renal insufficiency. We hypothesize that secondary FSGS results from a combination of postadaptive glomerular changes driven by increased lean body mass and potential direct nephrotoxic effects of anabolic steroids. Because of the expected rise in serum creatinine as a result of increased muscle mass in bodybuilders, this complication is likely underrecognized.

Endocytic delivery of lipocalin-siderophore-iron complex rescues the kidney from ischemia-reperfusion injury.

Neutrophil gelatinase-associated lipocalin (Ngal), also known as siderocalin, forms a complex with iron-binding siderophores (Ngal:siderophore:Fe). This complex converts renal progenitors into epithelial tubules. In this study, we tested the hypothesis that Ngal:siderophore:Fe protects adult kidney epithelial cells or accelerates their recovery from damage. Using a mouse model of severe renal failure, ischemia-reperfusion injury, we show that a single dose of Ngal (10 microg), introduced during the initial phase of the disease, dramatically protects the kidney and mitigates azotemia. Ngal activity depends on delivery of the protein and its siderophore to the proximal tubule. Iron must also be delivered, since blockade of the siderophore with gallium inhibits the rescue from ischemia. The Ngal:siderophore:Fe complex upregulates heme oxygenase-1, a protective enzyme, preserves proximal tubule N-cadherin, and inhibits cell death. Because mouse urine contains an Ngal-dependent siderophore-like activity, endogenous Ngal might also play a protective role. Indeed, Ngal is highly accumulated in the human kidney cortical tubules and in the blood and urine after nephrotoxic and ischemic injury. We reveal what we believe to be a novel pathway of iron traffic that is activated in human and mouse renal diseases, and it provides a unique method for their treatment.

Toxic acute tubular necrosis following treatment with zoledronate (Zometa).

BACKGROUND: Renal failure and toxic acute tubular necrosis (ATN) may be seen following exposure to a variety of therapeutic agents. Zoledronate (Zometa) is a new, highly potent bisphosphonate used in the treatment of hypercalcemia of malignancy. We report the first clinical-pathologic study of nephrotoxicity associated with this agent. METHODS: A cohort of six patients (four males and two females) with a mean age of 69.2 years received bisphosphonate therapy for multiple myeloma (five patients) or Paget's disease (one patient). In all patients, zoledronate was administered at a dose of 4 mg intravenously monthly, infused over at least 15 minutes, and the duration of therapy was mean 4.7 months (range, 3 to 9 months). RESULTS: All patients developed renal failure with a rise in serum creatinine from a mean baseline level of 1.4 mg/dL to 3.4 mg/dL. Renal biopsy revealed toxic ATN, characterized by tubular cell degeneration, loss of brush border, and apoptosis. Immunohistochemical staining revealed a marked increase in cell cycle-engaged cells (Ki-67 positive) and derangement in tubular Na+,K+-ATPase expression. Importantly, although all patients had been treated with pamidronate prior to zoledronate, no biopsy exhibited the characteristic pattern of collapsing focal segmental glomerulosclerosis observed in pamidronate nephrotoxicity. Following renal biopsy, treatment with zoledronate was discontinued and all six patients had a subsequent improvement in renal function (mean final serum creatinine, 2.3 mg/dL at 1 to 4 months of follow-up). CONCLUSION: The close temporal relationship between zoledronate administration and the onset of renal failure and the partial recovery of renal function following drug withdrawal strongly implicate this important and widely used agent in the development of toxic ATN.