Autosomal recessive polycystic kidney disease (ARPKD) is characterized by dilation of collecting ducts and by biliary dysgenesis and is an important cause of renal- and liver-related morbidity and mortality. Genetic analysis of a rat with recessive polycystic kidney disease revealed an orthologous relationship between the rat locus and the ARPKD region in humans; a candidate gene was identified. A mutation was characterized in the rat and screening the 66 coding exons of the human ortholog (PKHD1) in 14 probands with ARPKD revealed 6 truncating and 12 missense mutations; 8 of the affected individuals were compound heterozygotes. The PKHD1 transcript, approximately 16 kb long, is expressed in adult and fetal kidney, liver and pancreas and is predicted to encode a large novel protein, fibrocystin, with multiple copies of a domain shared with plexins and transcription factors. Fibrocystin may be a receptor protein that acts in collecting-duct and biliary differentiation.

The primary hyperoxalurias are rare disorders of glyoxylate metabolism in which specific hepatic enzyme deficiencies result in overproduction of oxalate. Due to resulting severe hyperoxaluria, recurrent urolithiasis or progressive nephrocalcinosis are the principal manifestations. End stage renal failure occurs frequently and is followed by systemic oxalate deposition with its devastating effects. Due to lack of familiarity with the primary hyperoxalurias and their heterogeneous clinical expression, the diagnosis is often delayed until there is advanced disease. In recent years, improvements in medical management have been associated with better patient outcomes. Though there are several therapeutic options that can help to prevent early kidney failure, to date the only curative treatment is combined liver-kidney transplantation in those patients with type I primary hyperoxaluria. Promising areas of investigation are being identified. Knowledge of the spectrum of disease expression, early diagnosis, and initiation of treatment before renal failure ensues are essential to realize a benefit for patients.

Abstract. Reported are the reduction of anti-HLA antibody levels and improvement of transplant rates by intravenous immunoglobulin (IVIG) in a randomized, double-blind, placebo-controlled clinical trial. Between 1997 and 2000, a total of 101 adult patients with ESRD who were highly sensitized to HLA antigens (panel reactive antibody [PRA] Ն50% monthly for 3 mo) enrolled onto an NIH-sponsored trial (IG02). Patients received IVIG or placebo. Subjects received IVIG 2 g/kg monthly for 4 mo or an equivalent volume of placebo with additional infusions at 12 and 24 mo after entry if not transplanted. If transplanted, additional infusions were given monthly for 4 mo. Baseline PRA levels were similar in both groups. However, IVIG significantly reduced PRA levels in study subjects compared with placebo. Sixteen IVIG patients (35%) and eight placebo patients (17%) were transplanted. Rejection episodes occurred in 9 of 17 IVIG and 1 of 10 placebo subjects. Seven graft failures occurred (four IVIG, three placebo) among adherent patients with similar 2-yr graft survival rates (80% IVIG, 75% placebo). With a median follow-up of 2 yr after transplant, the viable transplants functioned normally with a mean Ϯ SEM serum creatinine of 1.68 Ϯ 0.28 for IVIG versus 1.28 Ϯ 0.13 mg/dl for placebo. Adverse events rates were similar in both groups. We conclude that IVIG is better than placebo in reducing anti-HLA antibody levels and improving transplantation rates in highly sensitized patients with ESRD. Transplant rates for highly sensitized patients with ESRD awaiting kidney transplants are improved with IVIG therapy.Kidney transplantation is the preferred treatment for patients with ESRD. The benefits are evidenced by prolonged survival and improved quality of life for both children and adults. Despite these well documented benefits, transplant frequency remains lower than desirable as a result of limited organ availability (1,2). In patients with high levels of preformed anti-HLA antibodies (high panel reactive antibody [PRA]; highly sensitized), transplant rates are very low because of the additional immunologic barrier. Approximately 30% of patients on the waiting list are classified as sensitized, meaning they have peak PRA levels Ͼ20%, with about half of these having peak PRA levels Ͼ80%. These antibodies result from exposure to nonself HLA antigens; usually from previous transplants, blood transfusions, or pregnancy. Accordingly, women with ESRD are disproportionately sensitized compared with men.Patel and Terasaki (3) established in 1969 that the presence of anti-donor IgG antibody (positive crossmatch) was a contraindication for kidney transplantation. Accordingly, the higher the PRA, the more difficult it becomes to find an immunologically compatible match. Transplant rates are lower

Primary hyperoxaluria (PH) is a rare autosomal recessive disease characterized by oxalate accumulation in the kidneys and other organs. Three loci have been identified: AGXT (PH1), GRHPR (PH2), and HOGA1 (PH3). Here, we compared genotype to phenotype in 355 patients in the Rare Kidney Stone Consortium PH registry and calculated prevalence using publicly available whole-exome data. PH1 (68.4% of families) was the most severe PH type, whereas PH3 (11.0% of families) showed the slowest decline in renal function but the earliest symptoms. A group of patients with disease progression similar to that of PH3, but for whom no mutation was detected (11.3% of families), suggested further genetic heterogeneity. We confirmed that the AGXT p.G170R mistargeting allele resulted in a milder PH1 phenotype; however, other potential AGXT mistargeting alleles caused more severe (fully penetrant) disease. We identified the first PH3 patient with ESRD; a homozygote for two linked, novel missense mutations. Population analysis suggested that PH is an order of magnitude more common than determined from clinical cohorts (prevalence, approximately 1:58,000; carrier frequency, approximately 1:70). We estimated PH to be approximately three times less prevalent among African Americans than among European Americans because of a limited number of common European origin alleles. PH3 was predicted to be as prevalent as PH1 and twice as common as PH2, indicating that PH3 (and PH2) cases are underdiagnosed and/or incompletely penetrant. These results highlight a role for molecular analyses in PH diagnostics and prognostics and suggest that wider analysis of the idiopathic stone-forming population may be beneficial.

Adenine phosphoribosyltransferase (APRT) deficiency, cystinuria, Dent disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) and primary hyperoxaluria (PH) are rare but important causes of severe kidney stone disease and/or chronic kidney disease in children. Recurrent kidney stone disease and nephrocalcinosis, particularly in pre-pubertal children, should alert the physician to the possibility of an inborn error of metabolism as the underlying cause. Unfortunately, the lack of recognition and knowledge of the five disorders has frequently resulted in an unacceptable delay in diagnosis and treatment, sometimes with grave consequences. A high index of suspicion coupled with early diagnosis may reduce or even prevent the serious long-term complications of these diseases. In this paper, we review the epidemiology, clinical features, diagnosis, treatment and outcome of patients with APRT deficiency, cystinuria, Dent disease, FHHNC and PH with emphasis on childhood manifestations.