Abstract. Familial juvenile hyperuricemic nephropathy (FJHN [MIM 162000]) is an autosomal-dominant disorder characterized by abnormal tubular handling of urate and late development of chronic interstitial nephritis leading to progressive renal failure. A locus for FJHN was previously identified on chromosome 16p12 close to the MCKD2 locus, which is responsible for a variety of autosomal-dominant medullary cystic kidney disease (MCKD2). UMOD, the gene encoding the Tamm-Horsfall/uromodulin protein, maps within the FJHN/MCKD2 critical region. Mutations in UMOD were recently reported in nine families with FJHN/ MCKD2 disease. A mutation in UMOD has been identified in 11 FJHN families (10 missense and one in-frame deletion)-10 of which are novel-clustering in the highly conserved exon 4. The consequences of UMOD mutations on uromodulin expression were investigated in urine samples and renal biopsies from nine patients in four families. There was a markedly increased expression of uromodulin in a cluster of tubule profiles, suggesting an accumulation of the protein in tubular cells. Consistent with this observation, urinary excretion of wild-type uromodulin was significantly decreased. The latter findings were not observed in patients with FJHN without UMOD mutations. In conclusion, this study points to a mutation clustering in exon 4 of UMOD as a major genetic defect in FJHN. Mutations in UMOD may critically affect the function of uromodulin, resulting in abnormal accumulation within tubular cells and reduced urinary excretion.Familial juvenile hyperuricemic nephropathy (FJHN) is an autosomal-dominant disorder characterized by hyperuricemia and decreased urinary excretion of urate, followed by the development of chronic interstitial nephritis most often leading to progressive renal failure (1,2). The link between early hyperuricemia and subsequent progression of renal disease remains unclear.Urate is the end product of purine metabolism in humans, who have lost the expression of the uricase gene during evolution (3). Urate is freely filtered by the glomerulus and essentially reabsorbed, because only 10% of the filtered load is present in the final urine (4). The transport mechanisms of urate are localized in the proximal tubule (PT), whereas no experimental evidence supports urate permeability in the more distal segments of the nephron (5). URAT1, the long-hypothesized apical urate-anion exchanger involved in the reabsorption of urate by PT cells, was recently identified (6). Inactivating mutations of URAT1 located on 11q13 are responsible

Long-term function of kidney allografts depends on multiple variables, one of which may be the compatibility in size between the graft and the recipient. Here, we assessed the long-term consequences of the ratio of the weight of the kidney to the weight of the recipient (KwRw ratio) in a multicenter cohort of 1189 patients who received a transplant between 1995 and 2006. The graft filtration rate increased by a mean of 5.74 ml/min between the third and sixth posttransplantation months among patients with a low KwRw ratio (Ͻ2.3 g/kg; P Ͻ 0.0001). In this low KwRw ratio group, the graft filtration rate remained stable between 6 months and 7 years but then decreased at a mean rate of 3.17 ml/min per yr (P Ͻ 0.0001). In addition, low KwRw ratios conferred greater risk for proteinuria, more antihypertensive drugs, and segmental or global glomerulosclerosis. Moreover, a KwRw ratio Ͻ2.3 g/kg associated with a 55% increased risk for transplant failure by 2 years of follow-up. In conclusion, incompatibility between graft and recipient weight is an independent predictor of long-term graft survival, suggesting that avoiding kidney and recipient weight incompatibility may improve late clinical outcome after kidney transplantation.

After 1 year of follow-up, we observed no additional effect of rituximab in patients receiving PE, IVIg, and CS for AMR. Nevertheless, our study was underpowered and important differences between groups may have been missed. Complementary trials with long-term follow-up are needed.