Diagnosis of acute intermittent porphyria in a renal transplant patient: A case report.

BACKGROUND: Acute intermittent porphyria (AIP) is an inherited disorder of porphyrin metabolism with a worldwide distribution and a prevalence ranging from 1 to 9 per million population. AIP is caused by an autosomal dominant-inherited mutation of low penetrance resulting in a deficiency of porphobilinogen deaminase (PBGD) activity. Acute attacks are provoked by stressors such as certain medications, alcohol, and infection. We herein present the first case report of AIP detected in a post-renal transplant patient. CASE SUMMARY: The patient was a 65-year-old man who underwent transplantation 2 years previously for suspected nephroangiosclerosis and chronic interstitial nephro-pathy. He subsequently developed diabetes mellitus which required insulin therapy. He had been treated in the recent past with local mesalamine for proctitis. He presented with classic but common symptoms of AIP including intense abdominal pain, hypertension, and anxiety. He had multiple visits to the emergency room over a 6-mo period for these same symptoms before the diagnosis of AIP was entertained. His urinary postprandial blood glucose level was 60 mg/24 h (normal, < 2 mg/24 h). He was placed on a high carbohydrate diet, and his symptoms slowly improved. CONCLUSION: This case report describes a common presentation of an uncommon disease, in which post-transplant complications and medications may have contributed to precipitating the previously undiagnosed AIP. We hypothesize that the low-carbohydrate diet and insulin with which our patient was treated may have led to the attacks of AIP. Alternatively, our patient's mesalamine treatment for proctitis may have led to an acute AIP crisis. A high index of suspicion is needed to consider the diagnosis of a heme synthesis disorder, which presents with the common symptoms of abdominal pain, high blood pressure, and anxiety.

Elongation of the styloid processes in kidney-transplanted patients: The role of ectopic calcification as possible cause of Eagle syndrome.

Objective: To investigate the relationship between the presence of ectopic calcification in the elongation of the styloid process (SP) and its possible clinical manifestation (Eagle syndrome) in a population of kidney-transplant patients previously treated with hemodialysis.Methods: Digital orthopantomography of 92 kidney-transplanted patients and 68 control subjects were analyzed to measure the length of SPs. Calcium, phosphate, alkaline phosphatase, and parathyroid hormone (PTH) blood levels were also available for comparison.Results: The mean length of SPs was significantly different between groups, as were phosphate and PTH values.Discussion: Renal transplant patients who have been treated with hemodialysis present elongated SPs, presumably due to alterations in phosphate balance and PTH levels. Thus, in cases of orofacial pain in patients with a history of altered bone metabolism, particularly when due to renal insufficiency, Eagle syndrome should be suspected as the main cause of symptoms.

Dental Care for Patients with End-Stage Renal Disease and Undergoing Hemodialysis.

Chronic renal failure is a progressive disease characterized by a gradual destruction of nephrons and a consequent reduction of kidney function. End-stage renal disease (ESRD) necessitates renal replacement therapy as peritoneal dialysis, hemodialysis, or transplantation. Patients affected by ESRD or in hemodialysis are at risk for developing a number of comorbidities including hypertension, anemia, risk of bleeding, susceptibility to infection, medication side effects, and oral manifestations associated with the disease itself and with hemodialysis treatment. In this context, oral diseases represent a potential and preventable cause of poor health outcomes in people with ESRD due to their relation to infection, inflammation, and malnutrition. The aim of this article was to review ESRD and hemodialysis-associated manifestations and to describe the dental operative protocols for patients awaiting kidney transplantation in light of the most recent literature.

A nanoporous surface is essential for glomerular podocyte differentiation in three-dimensional culture.

Although it is well recognized that cell-matrix interactions are based on both molecular and geometrical characteristics, the relationship between specific cell types and the three-dimensional morphology of the surface to which they are attached is poorly understood. This is particularly true for glomerular podocytes - the gatekeepers of glomerular filtration - which completely enwrap the glomerular basement membrane with their primary and secondary ramifications. Nanotechnologies produce biocompatible materials which offer the possibility to build substrates which differ only by topology in order to mimic the spatial organization of diverse basement membranes. With this in mind, we produced and utilized rough and porous surfaces obtained from silicon to analyze the behavior of two diverse ramified cells: glomerular podocytes and a neuronal cell line used as a control. Proper differentiation and development of ramifications of both cell types was largely influenced by topographical characteristics. Confirming previous data, the neuronal cell line acquired features of maturation on rough nanosurfaces. In contrast, podocytes developed and matured preferentially on nanoporous surfaces provided with grooves, as shown by the organization of the actin cytoskeleton stress fibers and the proper development of vinculin-positive focal adhesions. On the basis of these findings, we suggest that in vitro studies regarding podocyte attachment to the glomerular basement membrane should take into account the geometrical properties of the surface on which the tests are conducted because physiological cellular activity depends on the three-dimensional microenvironment.

Small molecule membrane transporters in the mammalian podocyte: a pathogenic and therapeutic target.

The intriguingly complex glomerular podocyte has been a recent object of intense study. Researchers have sought to understand its role in the pathogenesis of common proteinuric diseases such as minimal change disease and focal segmental glomerular sclerosis. In particular, considerable effort has been directed towards the anatomic and functional barrier to macromolecular filtration provided by the secondary foot processes, but little attention has been paid to the potential of podocytes to handle plasma proteins beyond the specialization of the slit diaphragm. Renal membrane transporters in the proximal tubule have been extensively studied for decades, particularly in relation to drug metabolism and elimination. Recently, uptake and efflux transporters for small organic molecules have also been found in the glomerular podocyte, and we and others have found that these transporters can engage not only common pharmaceuticals but also injurious endogenous and exogenous agents. We have also found that the activity of podocyte transporters can be manipulated to inhibit pathogen uptake and efflux. It is conceivable that podocyte transporters may play a role in disease pathogenesis and may be a target for future drug development.

Percutaneous cryoablation of a renal cell carcinoma in a transplanted kidney.

In patients who undergo renal transplantation urinary tract tumors have an incidence of approximately 1.5%-3.3%. We report a rare case of renal cell carcinoma occurring in a transplanted kidney 25 years after the transplant. The lesion was treated by CT-guided percutaneous cryoablation with the ablation of renal lesion. This approach offers more accuracy compared with ultrasonography (US), and it is faster compared to magnetic resonance (MR) guidance. In transplanted kidneys CT-guided cryoablation seems to be safe.

Podocyte developmental defects caused by adriamycin in zebrafish embryos and larvae: a novel model of glomerular damage.

The zebrafish pronephros is gaining popularity in the nephrology community, because embryos are easy to cultivate in multiwell plates, allowing large number of experiments to be conducted in an in vivo model. In a few days, glomeruli reach complete development, with a structure that is similar to that of the mammalian counterpart, showing a fenestrated endothelium and a basement membrane covered by the multiple ramifications of mature podocytes. As a further advantage, zebrafish embryos are permeable to low molecular compounds, and this explains their extensive use in drug efficacy and toxicity experiments. Here we show that low concentrations of adriamycin (i.e. 10 and 20 µM), when dissolved in the medium of zebrafish embryos at 9 hours post-fertilization and removed after 48 hours (57 hpf), alter the development of podocytes with subsequent functional impairment, demonstrated by onset of pericardial edema and reduction of expression of the podocyte proteins nephrin and wt1. Podocyte damage is morphologically confirmed by electron microscopy and functionally supported by increased clearance of microinjected 70 kDa fluorescent dextran. Importantly, besides pericardial edema and glomerular damage, which persist and worsen after adriamycin removal from the medium, larvae exposed to adriamycin 10 and 20 µM do not show any myocardiocyte alterations nor vascular changes. The only extra-renal effect is a transient delay of cartilage formation that rapidly recovers once adriamycin is removed. In summary, this low dose adriamycin model can be applied to analyze podocyte developmental defects, such as those observed in congenital nephrotic syndrome, and can be taken in consideration for pharmacological studies of severe early podocyte injury.

Warfarin-related nephropathy: possible role for the warfarin pharmacogenetic profile.

Warfarin-related nephropathy (WRN) is a renal complication of warfarin treatment associated with over-anticoagulation. We describe a case of a 73-year-old man affected by chronic kidney disease, essential hypertension and atrial fibrillation treated with warfarin. The patient presented a rapid course of kidney failure after many episodes of over-anticoagulation, and renal biopsy demonstrated WRN. Interestingly, the patient's warfarin pharmacogenetic profile showed that he was warfarin sensitive. This is the first report describing the presence of gene polymorphisms affecting warfarin metabolism in a subject with a biopsy-proven WRN. The patient was treated with corticosteroids obtaining a partial clinical response.

Podocyte expression of membrane transporters involved in puromycin aminonucleoside-mediated injury.

Several complex mechanisms contribute to the maintenance of the intricate ramified morphology of glomerular podocytes and to interactions with neighboring cells and the underlying basement membrane. Recently, components of small molecule transporter families have been found in the podocyte membrane, but expression and function of membrane transporters in podocytes is largely unexplored. To investigate this complex field of investigation, we used two molecules which are known substrates of membrane transporters, namely Penicillin G and Puromycin Aminonucleoside (PA). We observed that Penicillin G pre-administration prevented both in vitro and in vivo podocyte damage caused by PA, suggesting the engagement of the same membrane transporters by the two molecules. Indeed, we found that podocytes express a series of transporters which are known to be used by Penicillin G, such as members of the Organic Anion Transporter Polypeptides (OATP/Oatp) family of influx transporters, and P-glycoprotein, a member of the MultiDrug Resistance (MDR) efflux transporter family. Expression of OATP/Oatp transporters was modified by PA treatment. Similarly, in vitro PA treatment increased mRNA and protein expression of P-glycoprotein, as well as its activity, confirming the engagement of the molecule upon PA administration. In summary, we have characterized some of the small molecule transporters present at the podocyte membrane, focusing on those used by PA to enter and exit the cell. Further investigation will be needed to understand precisely the role of these transporter families in maintaining podocyte homeostasis and in the pathogenesis of podocyte injury.

The role of basiliximab in the evolving renal transplantation immunosuppression protocol.

Basiliximab is a chimeric mouse-human monoclonal antibody directed against the alpha chain of the interleukin-2 (IL-2) receptor on activated T lymphocytes. It was shown in phase III trials to reduce the number and severity of acute rejection episodes in the first year following renal transplantation in adults and children, with a reasonable cost-benefit ratio. The drug does not increase the incidence of opportunistic infections or malignancies above baseline in patients treated with conventional calcineurin inhibitor-based immunosuppression. In the field of renal transplantation, basiliximab does not increase kidney or patient survival, despite the reduction in the number of rejection episodes. Basiliximab may reduce the incidence of delayed graft function. In comparison with lymphocyte-depleting antibodies basiliximab appears to have equal efficacy in standard immunological risk patients. Recently, IL-2 receptor monoclonal antibodies have been used with the objective of reducing or eliminating the more toxic elements of the standard immunosuppression protocol. Several trials have incorporated basiliximab in protocols designed to avoid or withdraw rapidly corticosteroids, as well as protocols which substitute target-of-rapamycin (TOR) inhibitors for calcineurin inhibitors.

Association of interferon-gamma +874A polymorphism with reduced long-term inflammatory response in haemodialysis patients.

BACKGROUND: We have studied the effects of interferon (IFN)-gamma allelic variations on expression levels of pro- and anti-inflammatory cytokines and on long-term inflammatory status in haemodialysis patients. METHODS: Genotyping was performed in 123 patients for single nucleotide polymorphisms in the first intron of the IFN-gamma gene (+874 T/A). They were prospectively followed for 2 years. Cytokine mRNA levels in whole blood cells (detected by real time (RT)-PCR technique) and serum C-reactive protein (CRP) concentrations were compared in patient groups with different IFN-gamma genotypes. Serum CRP was evaluated every month and inflammatory state was defined as percent of abnormal values (above 5 mg/l) over total determinations. Of the total, 102 patients survived and completed 24+/-1 monthly CRP determinations. The IFN-gamma +/-874 A/A, 'low-producer' genotype was associated with decreased (P<0.05) mRNA levels of IFN-gamma and of interleukin-6 and with a lower (P<0.05) frequency of CRP elevation (37+/-6%) than the +/-874 A/T and T/T, 'intermediate and high-producer' genotypes (59+/-6%, and 60+/-5%, respectively). The mRNA levels of tumor necrosis factor-alpha, IL-10 and of transforming growth factor-beta1 were not different in the three groups of patients. Pooled analysis in deceased (10+/-3 monthly CRP determinations) and survived patients confirmed the results obtained in the patients who completed the follow-up period. CONCLUSIONS: The 'low-producer' IFN-gamma +874 A/A genotype was associated with a preventive effect on long-term CRP elevation in haemodialysis patients possibly mediated by decreased gene expression of IFN-gamma and IL-6.

Glomerular permeability defect in hypertension is dependent on renin angiotensin system activation.

BACKGROUND: The aim of the present study was to compare glomerular permeability alterations associated with experimental hypertension models known to have different effects on the circulating renin-angiotensin system (RAS). METHODS: Five groups, 10 animals each, were studied. One group served as a nonhypertensive control. The other four groups of hypertensive animals were composed of spontaneously hypertensive rats, deoxycorticosterone acetate hypertensive rats, Goldblatt two-kidney, one-clip rats, and a group of Wistar rats infused with angiotensin II (200 ng/kg/min). Tail-cuff sphygmomanometric systolic blood pressure (BP), albumin permeability determined in isolated glomeruli exposed to oncotic gradients (P(alb)), glomerular filtration rate (GFR, iopamidol method), plasma renin activity (PRA), and albuminuria were evaluated. RESULTS: Alterations in P(alb) and albumin excretion rate were more evident in the experimental models with an activation of the RAS despite similar levels of systolic BP and GFR. A positive correlation was found between P(alb) and albuminuria (r = 0.51; P < .001) and between systolic BP and albuminuria (r = 0.37; P < .01). No relation was found between systolic BP and P(alb). CONCLUSIONS: The present study indicates that the activation of the RAS plays a significant role in the development of glomerular albumin permeability defects in hypertensive models and may contribute to the mechanisms that lead to target organ damage in hypertension.

Glomerular albumin permeability as an in vitro model for characterizing the mechanism of focal glomerulosclerosis and predicting post-transplant recurrence.

The putative mechanisms of proteinuria in idiopathic focal glomerulosclerosis and of its post-transplant recurrence are discussed. It is proposed that a balance between circulating factors with permeability activity on glomeruli and putative inhibitors play a key role. The characterization of inductors is currently in progress; most inhibitors appear to be apolipoproteins (mainly apoJ and apo E) but we cannot exclude other substances. The goal is now to evaluate the concentration of both inducers and inhibitors of glomerular permeability in vivo. Permeability activity in plasma of patients with FSGS with and without recurrence of the disease may be evaluated by an in vitro functional essay with isolated glomeruli. Published data on permeability activity evaluated with this method in different proteinuric states gave, however, controversial results and this test cannot be readily considered of clear clinical utility. Only the definitive characterization and quantification in vivo of the different molecules that play a role in FSGS may furnish adequate answer.

The effect of proteinase inhibitors on glomerular albumin permeability induced in vitro by serum from patients with idiopathic focal segmental glomerulosclerosis.

BACKGROUND: The putative circulating factor responsible for the glomerular permeability alterations induced in vitro by serum from patients affected by focal segmental glomerulosclerosis (FSGS) remains unidentified. We have observed that a serine proteinase isolated from patient serum increases albumin permeability in isolated glomeruli. The objective of the present study was to determine the effect of various proteinase inhibitors on glomerular albumin permeability (P(alb)) in isolated glomeruli incubated with FSGS serum. METHODS: The study population consisted of 12 FSGS patients (eight males; mean age: 21+/-10 years) previously shown to have elevated serum albumin permeability activity. P(alb) was determined by measuring the change in glomerular volume induced by applying oncotic gradients to isolated healthy rat glomeruli treated with patient serum in comparison to control serum. Solutions of seven different proteinase inhibitors (0.5 mg/ml) were added to the incubation media with the sera (1:1 vol/vol): serine proteinase inhibitors (PMSF, leupeptin, aprotinin, gabexate mesylate), the cysteine proteinase inhibitor E-64, the metalloproteinase inhibitor EDTA and the aspartate proteinase inhibitor pepstatin. Sera from the same patients were also tested with the addition to the incubation media of quinaprilat, an inhibitor of the metalloproteinase angiotensin-converting enzyme. RESULTS: Mean P(alb) of the sera was 0.86+/-0.11, with the addition of PMSF 0.41+/-0.09, leupeptin 0.30+/-0.17, aprotinin 0.09+/-0.14, gabexate mesylate 0.27+/-0.25, E-64 0.81+/-0.09, EDTA 0.68+/-0.10 or pepstatin 0.76+/-0.11. The mean P(alb) of the sera combined with quinaprilat was reduced to 0.34+/-0.35. Thus, only the serine proteinase inhibitors consistently blocked the increased P(alb) induced by the FSGS sera. CONCLUSIONS: In the cascade of events that lead to the initiation of glomerular fibrosis in FSGS, the putative glomerular permeability factor associated with FSGS may require a serine proteinase to effect its activity.

Apolipoprotein E in idiopathic nephrotic syndrome and focal segmental glomerulosclerosis.

BACKGROUND: Hyperlipemia characterizes nephrotic syndrome (NS) and contributes to the progression of the underlying nephropathy. The data in the literature support an implication of apolipoprotein E (apoE) in both hyperlipemia and focal segmental glomerulosclerosis (FSGS), a malignant condition associated with NS. METHODS: The apoE genotype was determined in 209 nephrotic patients, who were classified according to age and their response to steroids as resistant children (N = 96) and adults (43), and steroid dependent (33) and steroid responder (37) children. A total of 123 presented the histological features of FSGS. In a subgroup of 28 patients, serum and urinary levels of apoE and renal deposits were evaluated by immunofluorescence. RESULTS: The allelic frequencies of the three major haplotypes epsilon2, epsilon3, and epsilon4 were the same in nephrotic patients versus controls, and homozygosity for epsilon3epsilon3 was comparably the most frequent genotype (70 vs. 71%) followed by epsilon3epsilon4, epsilon2epsilon3, epsilon2epsilon4, epsilon4epsilon4. Serum levels of apoE were fivefold higher in NS and in FSGS patients than in controls, with a direct correlation with hypercholesterolemia and proteinuria. ApoE genotypes did not influence serum levels. Urinary levels were 1/10,000 of serum with an increment in nephrotic urines. Finally, immunofluorescence demonstrated the absence of apoE in sclerotic glomeruli, while comparably nephrotic patients with membranous nephropathy had an increased glomerular expression of apoE. CONCLUSIONS: ApoE is dysregulated in NS with a marked increment in serum, which is a part of the complex lipid metabolism. Down-regulation of glomerular apoE instead is a peculiarity of FSGS and may contribute to the pathogenesis of the disease. The normal distribution of apoE genotypes in nephrotic patients with FSGS excludes a pathogenetic role of genetic variants.

Nephrotic urine prevents increased rat glomerular albumin permeability induced by serum from the same patient with idiopathic nephrotic syndrome.

BACKGROUND: The putative humoral mediator thought to be involved in the pathogenesis of idiopathic nephrotic syndrome has not yet been identified. However, components exist in normal serum that block the permeability activity of FSGS serum in vitro. The potential of FSGS serum to increase glomerular albumin permeability may result from an imbalance between permeability factors and naturally occurring inhibitors. We hypothesized that this imbalance may be favoured by loss of inhibitory factors in nephrotic urine. METHODS: The study population consisted of seven patients with biopsy-proven FSGS, one with IgM nephropathy, and three with idiopathic nephrotic syndrome without biopsy, from whom frozen serum and dialysed and lyophilized urine samples were available. Glomerular albumin permeability (P(alb)) was determined from the change in glomerular volume induced by applying oncotic gradients across the basement membrane of normal isolated rat glomeruli pre-incubated with patient serum, normal control serum, patient serum mixed with an equal volume of urine from the same patient, or patient serum mixed with normal urine. Serum and urine apolipoproteins J and E were measured by dot-blot, utilizing peroxidase-labelled antibodies. The urinary capacity to scavenge oxygen radicals was determined after exposure of isolated glomeruli to superoxide generated by xanthine and xanthine oxidase. RESULTS: The mean P(alb) of the patients was markedly elevated at 0.74+/-0.08. The addition of urine from the same patient significantly reduced P(alb) (mean 0.15+/-0.23) in all but one of the patients with FSGS. Normal urine had no inhibitory effect in the 10 patients in which it was tested (mean 0.71+/-0.09). Serum apo J was slightly decreased and serum apo E was slightly increased compared with controls. Urine levels of both lipoproteins were significantly decreased compared with controls. Urine from FSGS patients effectively neutralized superoxide, whereas normal urine did not. CONCLUSIONS: Nephrotic urine but not normal urine contains components that block increased albumin permeability in isolated rat glomeruli induced by serum from patients with the idiopathic nephrotic syndrome. The inhibitory function of these components, which appear not to include apolipoproteins J and E, may involve scavenging of superoxide as a final common pathway. Loss in the urine from the serum of naturally occurring inhibitors in the initial stages of the disease may propagate proteinuria and glomerular injury.

Serum glomerular permeability activity in patients with podocin mutations (NPHS2) and steroid-resistant nephrotic syndrome.

A plasma factor displaying permeability activity in vitro and possibly determining proteinuria has been hypothesized in idiopathic focal segmental glomerulosclerosis (FSGS). In vitro permeability activity (P(alb)) was determined in sera of five patients with autosomal recessive steroid-resistant nephrotic syndrome (NPHS2), an inherited condition indistinguishable from idiopathic FSGS on clinical grounds, but in which proteinuria is determined by homozygous mutations of podocin, a key component of the glomerular podocyte. All patients had presented intractable proteinuria with nephrotic syndrome; four developed renal failure and received a renal allograft. For comparison, sera from 31 children with nephrotic syndrome were tested. Pretransplant P(alb) was high in all cases (mean 0.81 +/- 0.06), equivalent to levels observed in idiopathic FSGS. Overall, P(alb) did not correlate with proteinuria. The posttransplant outcome was complicated in two patients by recurrence of proteinuria after 10 and 300 d, respectively, that responded to plasmapheresis plus cyclophosphamide. P(alb) levels were high at the time of the recurrence episodes and steadily decreased after plasmapheresis, to reach normal levels in the absence of proteinuria after the seventh cycle. In an attempt to explain high P(alb) in these patients, putative inhibitors of the permeability activity were studied. Coincubation of serum with homologous nephrotic urine reduced P(alb) to 0, whereas normal urine did not determine any change, which suggests loss of inhibitory substances in nephrotic urine. The urinary levels of the serum P(alb) inhibitors apo J and apo E were negligible in all cases, thus suggesting that other urinary inhibitors were responsible for the neutralizing effect. These data indicate that P(alb) is high in NPHS2, probably resulting from loss of inhibitors in urine. Lack of correlation of P(alb) with proteinuria suggests a selective loss of inhibitors. As in idiopathic FSGS, proteinuria may also recur after renal transplantation in NPHS2 patients, and post-transplant proteinuria is associated with high P(alb). The relationship between elevated P(alb) and proteinuria in NPHS2 remains to be determined.

Characterization of plasma factors that alter the permeability to albumin within isolated glomeruli.

Focal segmental glomerulosclerosis (FSGS) is responsible for intractable proteinuria and has become the leading cause of renal insufficiency in children. Protenuria in FSGS is probably due to the effect of one or more permeability plasma factors which increase the glomerular permeability to proteins. We fractioned serum from children with FSGS using two mixed chromatographic-electrophoretic approaches and have purified ten proteins among several hundreds which maintained the original permeability activity after renaturation, utilizing an isolated rat glomeruli assay. Six proteins were successfully characterized by mass spectometry as fibulin, apolipoprotein J, vitronectin, albumin isoforms, gamma chain fibrinogen and mannan-binding lectin-associated serine protease. Both procedures utilized for purification were based on affinity chromatography with Protein A-Sepharose and ended with two-dimensional electrophoresis, whereas the intermediate steps were different. Cross inhibition with zinc and aprotinin of purified factors and whole FSGS serum indicate strong homology. These are the first data demonstrating permeability activity for serum proteins, an observation with important implications in pathogenesis of proteinuria. Determination of the serum levels of each protein and a careful differentiation of FSGS from normal serum could provide the basis for clarifying the mechanism of proteinuria.

Prevalence, genetics, and clinical features of patients carrying podocin mutations in steroid-resistant nonfamilial focal segmental glomerulosclerosis.

Podocin mutations (NPHS2 gene) are responsible for the autosomal recessive form of steroid-resistant nephrotic syndrome. As a result of a screening for these gene alterations in a cohort of Italian patients with nonfamilial nephrotic syndrome and histologic focal segmental glomerulosclerosis (FSGS), nine patients with NPHS2 gene homozygous or composite heterozygous mutations were found. In addition to the previously described defects, two novel mutations at exon 4 were identified (frameshift, L169P); four single nucleotide polymorphisms (SNPs) and one dinucleotide repeat were also identified. On the basis of haplotype analysis, a founder effect was suggested for the 419delG mutation, the most frequently observed in the patients studied. Patients carrying NPHS2 mutations and without a family history of nephrotic syndrome were indistinguishable from those with idiopathic FSGS on the basis of the clinical phenotype. Two of the nine patients had normal renal function at 3 and 10 yr of age, despite the presence of the nephrotic syndrome. The other seven had reached end-stage renal failure at a mean age of 9.6 yr (range, 4 to 17 yr) and had received renal allografts. In those presenting with end-stage renal failure, the clinical and laboratory features both before and after transplantation were similar, including the age at onset, the amount of proteinuria, and the absence of any response to steroids and other immunosuppressants. Finally, two children presented recurrence of mild proteinuria after transplantation, which promptly remitted after plasmapheresis combined with cyclophosphamide. These data demonstrate that podocin mutations in nonfamilial cases of steroid-resistant nephrotic syndrome are frequent and may be due in one case to a founder effect. The pretransplantation and posttransplantation outcomes in the group of patients with mutations of the podocin gene are similar to classical idiopathic FSGS, including the possibility of recurrence of proteinuria that is mild and responsive to plasmapheresis. These observations support a role of molecular screening of the podocin gene in patients with nephrotic syndrome before immunosuppressive treatment is started.

Apolipoproteins prevent glomerular albumin permeability induced in vitro by serum from patients with focal segmental glomerulosclerosis.

Glomerular albumin permeability alterations can be induced in vitro by serum from patients with end-stage renal disease caused by primary focal segmental glomerulosclerosis (FSGS). It was hypothesized that inhibitory substances may be present in normal serum, which may prevent the permeability alterations in isolated glomeruli, and the present study sought to isolate and characterize these factors. Albumin permeability was determined from the change in glomerular volume induced by applying oncotic gradients across the basement membrane of healthy isolated rat glomeruli preincubated with FSGS serum and normal serum fractionated using standard techniques. Fractions of normal serum with inhibitory activity obtained by a multistep chromatographic procedure underwent two-dimensional electrophoresis and staining. Approximately 50 protein spots were recovered, renatured, and tested for antipermeability activity. Five of these proteins demonstrated consistent inhibitory activity, and desorption ionization and mass spectrometry proved them to be components of high-density lipoprotein: apolipoproteins (apo) E(2) and E(4), high-molecular-weight J and L, and a 28-kD fragment of A-IV. Polyclonal antibodies to apo E or apo J added to the whole normal serum restored the permeability activity of the FSGS serum in the bioassay. Commercially available apo E and apo J also demonstrated antipermeability activity when added to FSGS serum. Cyanogen bromide digestion of apo A-IV produced fragments that inhibited the permeability activity of the FSGS serum, whereas the intact protein did not. Thus, components of high-density lipoprotein are capable of preventing glomerular albumin permeability induced by serum from patients with FSGS in an in vitro system. The specificity and mechanism of the inhibition remain to be determined; the alteration of normal inhibitory activity in vivo may be a component in the pathophysiology of FSGS.