An extremely mild clinical course in a case with LAMB2-associated nephritis diagnosed with next-generation sequencing.

Biallelic pathogenic variants in the laminin ß2 (LAMB2) gene, which encodes laminin ß2, are associated with Pierson syndrome characterized by a congenital nephrotic syndrome that rapidly progresses to end-stage renal disease, distinct ocular maldevelopment with bilateral microcoria, and neurodevelopmental deficits. However, the phenotypic spectrum of LAMB2-associated disorder is broader than expected, and cases with milder phenotypes such as isolated congenital or infantile nephrotic syndrome have also been reported. We report a patient with LAMB2-associated renal disorder showing an extremely mild phenotype. A 5-year-old girl presented with asymptomatic proteinuria and hematuria detected by urinalysis screening. She had been previously healthy without any additional renal symptoms. The serum albumin and creatinine levels were normal. Renal biopsy revealed minor glomerular abnormalities with occasional focal mesangial proliferation. Electron microscopy showed no structural changes in the glomerular basement membrane. Targeted sequencing of podocyte-related genes using next-generation sequencing was performed. As a result, previously reported biallelic pathogenic variants of the truncating variant (c.5073_5076dupCCAG) and a splice site variant (c.3797 + 5G > A) in the LAMB2 gene were detected, and the patient was diagnosed with LAMB2-associated renal disorder. Interestingly, a previously reported case with this splicing variant also showed an atypically mild phenotype. We suggest that clinicians should consider LAMB2-associated nephritis as an important differential diagnosis in children with asymptomatic proteinuria and microscopic hematuria if there is no structural change in the glomerular basement membrane. A comprehensive gene-screening system using next-generation sequencing is useful for diagnosing these atypical cases with isolated urine abnormalities.

Optimal urinary protein-to-creatinine ratio as a renal biopsy criterion in children with asymptomatic proteinuria.

BACKGROUND: This retrospective case series aimed at exploring the optimal urinary protein-to-creatinine ratio (uP/uCr) cut-off value to determine the need for renal biopsy in pediatric patients with isolated asymptomatic proteinuria (ASP). METHODS: Data from 32 patients (16 boys, 16 girls) with persistent isolated ASP treated between January 2001 and September 2010 were analyzed. The uP/uCr cut-off value at which a renal biopsy is indicated was determined using the minimum p-value approach. An "optimal" cut-off value was selected to distinguish significant and non-significant glomerular changes. RESULTS: The minimum p-value approach using the χ2-test resulted in a peak uP/uCr of 0.5 g/g x Cr, which was then used to divide the patients into a low-proteinuria group and a high-proteinuria group. The proportion of significant glomerular changes was marginally higher (p = 0.097) in the high-proteinuria group than in the low-proteinuria group after adjustment for multiple tests. In addition, the number of patients with severe proteinuria at the most recent followup was higher in the high-proteinuria group than in the low-proteinuria group. CONCLUSION: The use of a uP/uCr >= 0.5 g/g x Cr may be a reasonable criterion for renal biopsy aimed at distinguishing renal outcomes in patients with persistent isolated ASP.

Synergistic protective effects of mizoribine and angiotensin II receptor blockade on cyclosporine A nephropathy in rats.

BACKGROUND: Chronic cyclosporine A (CsA) nephrotoxicity is manifested by renal dysfunction, progressive histopathological kidney lesions characterized by afferent arteriolopathy, and tubulointerstitial fibrosis. In addition to the direct toxic effect of CsA, many other etiological factors such as angiotensin II, transforming growth factor (TGF)-ß, and macrophage infiltration are involved in this pathogenesis. This study investigated the hypothesis that concomitant administration of mizoribine (MZR) and angiotensin II receptor blockade (ARB) may prevent CsA nephrotoxicity in rats. METHODS: Sprague-Dawley male rats were divided into the following seven groups: group 1, treated with CsA; group 2, treated with CsA + MZR; group 3, treated with CsA + valsartan (Val); group 4, treated with CsA + MZR + Val; group 5, treated with MZR; group 6, treated with Val; and group 7, controls (n = 5 each). Renal histopathology and the effect of CsA-induced nephrotoxicity on inflammatory mediators were evaluated. RESULTS: Results of this study demonstrated that ARB administration significantly decreased arteriolopathy and that in comparison with monotherapy, concomitant administration of MZR and ARB further decreased arteriolopathy, fibrosis, macrophage infiltration, and TGF-ß1 mRNA expression associated with CsA nephrotoxicity. CONCLUSION: These findings indicate that MZR and ARB combination treatment provides synergistic protective effects against chronic CsA nephrotoxicity.

Membranoproliferative glomerulonephritis Type 3 associated with Kabuki syndrome.

First described in Japanese patients, Kabuki syndrome (KS) is a congenital condition associated with multiple anomalies and mental retardation. Although urological and immune abnormalities are common in KS, immune complex nephritis such as membranoproliferative glomerulonephritis (MPGN) has not yet been reported. We describe the first reported case of a KS patient with common variable immunodeficiency (CVI) and recurrent otitis media who developed severe proteinuria and hematuria due to MPGN Type 3 detected during the school urinary screening program in Japan. The patient was intravenously treated with methylprednisolone pulses followed by alternate-day prednisolone and an angiotensin receptor blocker. The patient showed remarkable improvement in both histological and urinary analyses. This case report suggests that immune abnormalities associated with KS can play an important role in the development of MPGN. Urinalysis should be regularly performed in KS patients with hypogammaglobulinemia and/or recurrent infection.

Is there a pathogenic association between Fabry's disease and IgA nephropathy?

Several cases of concurrent Fabry's disease and IgA nephropathy have been reported, but the pathogenic association between these two diseases remains unclear. This is a report on the case of a girl with severe IgA nephropathy who was subsequently diagnosed with subclinical Fabry's disease. An 11-year-old girl was admitted to our hospital with massive proteinuria and hematuria detected by urinary screening. An initial renal biopsy revealed severe IgA nephropathy with diffuse mesangial proliferation. She was treated with intravenous methylprednisolone pulses followed by 2 years of oral steroids. The treatment improved both the urinary abnormalities and the second renal biopsy findings. At the age of 15 years, mild proteinuria prompted us to perform a third renal biopsy, and histology revealed minor glomerular abnormalities. In addition, numerous myelin-like bodies were detected in podocytes by electron microscopy. The histological findings combined with the low level of α-galactosidase A activity led to the diagnosis of concomitant Fabry's disease with IgA nephropathy. Our experience suggests that the initial massive proteinuria was not due to Fabry's disease, but was rather a manifestation of coincidental IgA nephropathy. We speculate that the coexistence of IgA nephropathy and Fabry's disease occurred by chance.

Nephrotoxicity of once-daily cyclosporine A in minimal change nephrotic syndrome.

BACKGROUND: Although once-daily cyclosporine (CsA) therapy may have greater nephrotoxic-sparing effects than standard twice-daily therapy, little information is available in children with steroid-dependent minimal change nephrotic syndrome (MCNS) regarding histological analysis after long-term once-daily administration. CASE-DIAGNOSIS/TREATMENT: A prospective study of the clinical efficacy and comparison between pre- and post-treatment renal biopsy findings in ten children (mean age, 8.8 years) with steroid-dependent MCNS who were administered once-daily CsA therapy for more than 24 months (mean ± SD, 30 ± 3.7) was performed in Saitama Children's Medical Center. Administration of once-daily CsA therapy (mean dose, 2.8 ± 0.6 mg/kg/day; mean C2 levels, 670 ± 64 ng/ml) resulted in a significant reduction in the median relapse rate from 4.6 to 0.2 times per year, and five patients did not experience a relapse of NS. Furthermore, mean threshold of prednisolone dose significantly reduced from 1.2 to 0.02 mg/kg on alternate days. However, two patients showed evidence of chronic CsA nephrotoxicity (CsAN). CONCLUSIONS: Once-daily CsA therapy appears to be effective in children with steroid-dependent MCNS. However, follow-up renal biopsies should be performed to investigate the presence of CsAN after more than 24 months of treatment with once-daily regimen as well as with the conventional twice-daily regimen.

Protective effects of Mizoribine on Cyclosporine A nephropathy in rats.

The therapeutic benefits of Cyclosporine A (CsA) are often limited by the chronic nephrotoxicity of its long-term use. Chronic nephrotoxicity is manifested by renal function impairment and progressive histopathological kidney lesions characterized by tubular vacuolization, tubular necrosis, interstitial fibrosis, and afferent arteriolopathy. This study tested the hypothesis that the concurrent administration of Mizoribine (MZR) may improve chronic CsA nephrotoxicity. Sprague-Dawley male rats were divided into the following four groups: group 1, control (n = 6); group 2, treated with CsA alone (n = 5); group 3, treated with CsA and MZR (n = 4); and group 4, treated with MZR alone (n = 6). The anti-inflammatory and antifibrotic effects of MZR were studied by evaluating the concentrations of the inflammatory mediator, osteopontin, renal function, and histopathology. The interstitial fibrosis was stained blue with Elastica-Massontrichrome and the sections were quantified. The CsA-treated rats showed decreased renal function and increased histologic parameters in comparison with the control rats and also showed significantly increased interstitial fibrosis area and macrophage in comparison with the control rats. The CsA MZR treatment significantly improved the interstitial fibrosis area and macrophage in comparison with the CsA-treated rats. On the basis of these findings, we suggest MZR effectively attenuates renal macrophage accumulation and the progression of interstitial fibrosis.

Multiple drug-resistant gene 1 in children with steroid-sensitive nephrotic syndrome.

BACKGROUND: A full dose of corticosteroid is required to induce complete remission (CR) in steroid-sensitive nephrotic syndrome (SSNS), unless it is possible to taper and discontinue along with the course after CR. But the mechanism of this change in steroid sensitivity remains unknown. P-glycoprotein (PGP) can eliminate given corticosteroids from cytoplasm, which results in corticosteroid resistance. Therefore, drug delivery was analyzed using real-time polymerase chain reaction (PCR) of multiple drug-resistant gene 1 (MDR1; encoding PGP) mRNA expression. METHODS: Fourteen patients with SSNS (male/female: 14/0; age: 1-23 years; mean 10.4 years) were enrolled in the study. MDR1 mRNA gene expression of peripheral blood nucleated cells (PBNC), before and after CR (19 sets of blood samples), was quantified using real-time PCR. RESULTS: The MDR1 mRNA levels before CR were variable in each patient, but there was an apparent decrease in the MDR1 gene expression of PBNC after CR (P < 0.003). CONCLUSION: PGP may play a role in the tapering of corticosteroids after CR in SSNS.

Plasma exchange combined with immunosuppressive treatment in a child with rapidly progressive IgA nephropathy.

Although diffuse crescentic formation in immunoglobulin A (IgA) nephropathy, histologically characterized by extensive extracapillary proliferation, is assumed to have a poor prognosis, there has still been no established treatment because of the low prevalence of the condition, especially in pediatric patients. This paper reports on a 5-year-old boy with rapidly progressive IgA nephropathy requiring dialysis for 1 month. He had been treated with plasma exchange (PE) combined with immunosuppressive treatment, including steroids and mizoribine, because renal function deteriorated rapidly despite initial treatment with intravenous methylprednisolone pulse. The histological findings at that time revealed IgA nephropathy, with large circumferential cellular crescent formation in approximately 80% of the glomeruli. Three weeks after PE initiation, serum levels of creatinine and IgA-containing immune complexes returned to normal, and urinary protein excretion gradually decreased. The second renal biopsy taken 7 months later demonstrated mild IgA nephropathy with small fibrocellular crescents. This case report indicates that PE combined with immunosuppressive treatment may benefit children with rapidly progressive IgA nephropathy, even when extensive crescent formations are present.

Triggers of relapse in steroid-dependent and frequently relapsing nephrotic syndrome.

An awareness of the triggers of relapse is critical for the control of steroid-dependent, frequently relapsing nephrotic syndrome (SDFRNS). We have investigated the triggers, usually described as 'episodes', to such relapses within a temporal context. Thirty-five patients with SDFRNS were analyzed retrospectively. A total of 442 relapses occurred in 2499 patient-months. The relapses were classified into two groups: those with episodes (E+) and those without episodes (E-). There were 135 E+ relapses and 296 E- relapses. The common cold was the most common episode (52%) of E+ relapse, followed by school events (18%). These E+ relapses occurred almost evenly throughout the 4 weeks between each follow-up visit. Conversely, 161 (55%) of the 296 E-z relapses occurred within the 3-day period preceding the patient's appointment (relapse-related hospital visit, RRHV). McNemar's test revealed that the concentration of relapses in this period was statistically significant (P < 0.00011). In addition, 15 out of 26 RRHV without additional therapy showed a spontaneous remission. From a chronological perspective, the common cold and school events as well as up-coming hospital visits may trigger relapses in SDFRNS patients.

Cockayne syndrome with recurrent acute tubulointerstitial nephritis.

A 12-year-old girl, who had been diagnosed as having Cockayne syndrome (CS), was admitted for emaciation and dehydration. On admission the patient had mild chronic renal failure (glomerular filtration rate: GFR 50 mL/min) and hyperuricemia. After rehydration, allopurinol was commenced for her hyperuricemia. Then, her renal function rapidly deteriorated (GFR 20 mL/min) with enhancement of proximal tubular dysfunction and hypertension. A renal biopsy showed that the patient had acute tubulointerstitial nephritis (ATIN). Based on this diagnosis, allopurinol was stopped and prednisolone was started (2 mg/kg per day), following which the renal tubular function improved. However, the proteinuria intensified to become nephrotic syndrome. After 1 month the patient developed a gastric ulcer. Famotidine was commenced but GFR deteriorated and renal proximal tubular dysfunction re-occurred. The renal pathology was evaluated by referring to the previous reports of renal pathology in CS. It is suggested that rapid deterioration of the renal function in CS patients might be the result of ATIN. In addition, the present nephrotic syndrome seemed to be accompanied by ATIN, as in other reports.

Charge selective function in childhood glomerular diseases.

The charge selectivity (CS) function in human renal disease has not been unequivocally demonstrated to date. However, the clearance ratio of IgA to IgG may be theoretically useful in estimating CS in humans, since IgA and IgG have similar sizes and tertiary structures, but distinct isoelectric points (3.5-5.5 [IgA] and 4.5-9.0 [IgG]), and Stokes-Einstein radius: 61 A (IgA) and 49-60 A (IgG). Two-dimensional electrophoresis with the following immunoblotting revealed that the considerably anionic portion (isoelectric points [pI] <4.0) of IgA, visible in serum, was absent in the urine in steroid-sensitive nephrotic syndrome (SSNS) but present in the same during IgA nephropathy (IgAN) and membranoproliferative glomerulonephritis (MPGN). A latex assay revealed the CS index (CSI) was significantly low in patients with podocyte disease (group A), including SSNS, focal and segmental glomerulosclerosis (FSGS) and Finnish-type congenital nephrotic syndrome (FCNS), but high in those with Alport syndrome (AS), IgAN, Henoch-Schönlein purpura nephritis (HSPN), and MPGN (group B). The linear regression analysis of the IgA size selectivity index (IgA SSI; clearance ratio of IgA to transferrin) and SSI (clearance ratio of IgG to transferrin), which represents the clearance ratio of IgA to IgG referring to the transferrin clearance, revealed the influence of the charge more accurately. Indeed, the slope of the regression lines of IgA SSI (y) to SSI (x) were concluded to be y = 0.39x (group A) and y = 1.05x (group B), respectively. These results suggested that the charge selective barrier among podocyte diseases (group A) is preserved to some degree, but lost in cases of nephritis and AS (group B).

Thin basement membrane nephropathy associated with minimal change disease in a 15-year-old boy.

Thin basement membrane nephropathy (TBMN) is characterized clinically by persistent hematuria, minimal proteinuria, normal renal function, another family member with hematuria, and a benign course. Especially in childhood TBMN, proteinuria of any degree is reported to be uncommon. We report on a boy with benign familial hematuria found by urinary screening at 3 years of age who presented with nephrotic syndrome (NS) at 15 years of age. His renal histology showed TBMN associated with minimal change disease (MCD). Treatment with corticosteroid resulted in complete remission of NS in a short period of time, while isolated hematuria persisted during the follow-up period despite this therapy. We speculate, therefore, that the nephrotic range proteinuria is not due to TBMN but rather is the manifestation of associated MCD. Several cases of TBMN with NS have been reported in adults, but it has not yet been reported in children in the literature. To our knowledge, this is the first case of childhood TBMN associated with NS resulting from coincidental MCD.

Molecular genetic alterations and gene expression profile of a malignant rhabdoid tumor of the kidney.

Malignant rhabdoid tumor of the kidney (MRTK) is a rare but highly aggressive tumor in children, and knowledge about the molecular signature of this tumor is limited. We report the molecular genetic alterations and gene expression profile of an MRTK tumor that arose in a 4-month-old Japanese girl. Fluorescence in situ hybridization and Southern blot analyses revealed a homozygous deletion of an approximately 0.29-Mb genomic region bordered by the Rgr and DDT genes in these tumor cells. This deleted region encodes SMARCB1, a candidate tumor suppressor gene for MRTK. Using a high-density oligonucleotide DNA array, we found increased expression of 25 genes, including genes involved in the cell cycle (10 genes), DNA replication (3 genes), cell growth (5 genes), and cell proliferation (5 genes), in this MRTK tumor sample, compared with a noncancerous kidney (NK) sample. On the other hand, 64 genes, including 4 genes regulating apoptosis, were found to show decreased expression in this MRTK tumor sample, compared with the NK sample. Among these alterations, we found alterations of expression of some genes, such as IGF2, MDK, TP53, and TNFSF10, in this MRTK tumor, as described previously. The molecular genetic alterations and altered pattern of gene expression found in this case may have contributed to the biological characteristics of the MRTK tumor that arose in our patient.

High-dose mizoribine therapy for childhood-onset frequently relapsing steroid-dependent nephrotic syndrome with cyclosporin nephrotoxicity.

Cyclosporin A (CsA) is an effective treatment for frequently relapsing steroid-dependent nephrotic syndrome (FR-SDNS), but its use can be complicated by renal toxicity and a high incidence of relapses after withdrawal. We report 9 adolescent patients with childhood-onset FR-SDNS who had been treated with long-term CsA that resulted in moderate-to-severe CsA nephropathy (CsAN). They were treated with high-dose (mean: 10.1 mg/kg per day) mizoribine (MZR) in an attempt to allow weaning of CsA and/or steroid therapy, and reduce the frequency of relapses. Seven out of 9 patients were weaned off CsA by 1-year follow-up, although in the remaining 2 patients, MZR did not show any beneficial effects. Overall, this high-dose MZR therapy results in significant steroid sparing and reduction in relapse rates in our patients. Our experience shows that high-dose MZR therapy in patients with FR-SDNS who are also CsA-dependent appears to be effective in reducing CsA exposure as well as in decreasing the frequency of relapses.