Increased chymase-positive mast cells in children with crescentic glomerulonephritis.

Mast cell-derived chymase is an angiotensin II-forming enzyme that appears to be involved in tubulointerstitial fibrosis in the kidneys. Previous studies have shown that the level of chymase increases in grafted kidneys after rejection and in adult patients with diabetic nephropathy. However, the significance of chymase in children with renal diseases has not been investigated. Using immunohistochemistry, we have investigated chymase expression in biopsy samples of renal tissue from 104 children with kidney diseases, including rapidly progressive crescentic glomerulonephritis (n = 3), diabetic nephropathy (n = 2), allografted kidney (n = 3), membranoproliferative glomerulonephritis (n = 6), immunoglobulin A nephropathy (n = 33) and Henoch-Schönlein purpura nephritis (n = 23). Increased numbers of chymase-positive mast cells were observed in the renal cortex of all three patients with crescentic glomerulonephritis (mean 26.0/mm(2); range 19.3-36.8/mm(2)). Chymase-positive cells were also observed in the renal biopsy of an allografted kidney and in those from children with diabetic nephropathy. The mean number of chymase-positive cells in renal tissue samples characterized by each renal disease was significantly correlated with the mean intensity of the interstitial fibrosis in that same tissue sample (Spearman's rank correlation test p = 0.0013; rank correlation coefficient 0.84). These findings suggest that mast cell-derived chymase plays an important role in juvenile crescentic glomerulonephritis.

Membranous nephropathy associated with thyroid-peroxidase antigen.

A 6-year-old previously healthy Japanese girl was found to have dipstick 2+ proteinuria and a goiter based on the results of a routine school medical examination. Her serum free-thyroxine level was 4.98 ng/dL (normal range 0.95-1.74 ng/dL), thyroid-stimulating hormone (TSH) was less than 0.003 microU/mL (0.34-3.88 microU/mL), anti-microsomal (anti-thyroid-peroxidase) antibody was 1600 T (up to 100), anti-thyroglobulin antibody was 400 T (up to 100), and TSH-receptor antibody was 84% (up to +/-10%). These results are consistent with a diagnosis of Graves' disease. Electron microscopy examination of a renal biopsy specimen revealed electron-dense deposits located in the subepithelial spaces, and immunofluorescence microscopy examination demonstrated bright granular stainings of immunoglobulin G along the glomerular capillary walls. These findings are characteristic of membranous nephropathy. To investigate the relationship between the membranous nephropathy and Graves' disease, we carried out a second immunofluorescence study, which revealed that the immunoglobulin G granular deposits corresponded to glomerular granular staining of thyroid-peroxidase, whereas staining for thyroglobulin was absent. It was therefore assumed that the deposition of immune complexes mediated by thyroid-peroxidase had caused the membranous nephropathy in this patient. This is the first report of membranous nephropathy associated with Graves' disease in which deposits of thyroid-peroxidase, rather than thyroglobulin, have been confirmed in the kidney.

Improved renal survival in Japanese children with IgA nephropathy.

Since the beginning of the 1990s, Japanese medical practitioners have extensively prescribed angiotensin-converting enzyme (ACE) inhibitors for children with mild IgA nephropathy (IgA-N) and steriods for those with severe IgA-N. We have performed a retrospective cohort study to clarify whether the long-term outcome has improved in Japanese children with IgA-N. Renal survival was defined as the time from onset to end-stage renal disease (ESRD). We divided the study period into two time periods based on the occurrence of the initial renal biopsy:1976-1989 and 1990-2004. Actuarial survivals were calculated by Kaplan-Meier method, and comparisons were made with the logrank test. The Cox proportional hazard model was used for multivariate analysis. Between 1976 and 2004, 500 children were diagnosed as having IgA-N in our hospitals. The actuarial renal survival from the time of apparent disease onset was 96.4% at 10 years, 84.5% at 15 years and 73.9% at 20 years. Renal survival in the 1990-2004 period was significantly better than that in 1976-1989 (p=0.008), and a marked improvement in renal survival in patients with severe IgA-N was also observed (p=0.0003). Multivariate analysis indicated that diagnosis year was a significant factor for ESRD-free survival independently of baseline characteristics. The results of this study show that there has been an improvement in terms of renal survival in Japanese children with IgA-N.

Segmental membranous glomerulonephritis in children: comparison with global membranous glomerulonephritis.

Generally, idiopathic membranous glomerulonephritis (MGN) is a global glomerular disease that affects the whole of the glomerulus. However, idiopathic segmental MGN (SMGN) that shows IgG deposits in a portion of the glomerulus is encountered often. For clarification of whether SMGN is the same entity as idiopathic global MGN (GMGN), the two diseases were compared. From 1978 to 2004, 38 children (11 with SMGN and 27 with GMGN) received a diagnosis of idiopathic MGN. Immunofluorescence microscopy showed segmental granular IgG staining along the capillary loops in SMGN, whereas GMGN showed global staining. On light microscopy, SMGN showed segmental thickening of the glomerular basement membrane, with spike formation, whereas GMGN showed global lesions. The frequency of C1q deposits in SMGN was significantly higher than that in GMGN (91 versus 41%; P < 0.01). On electron microscopy, mesangial electron-dense deposits were detected in 10 (91%) cases of SMGN and also were found in the subepithelial and intramembranous area, whereas only six (22%) cases of GMGN had mesangial electron-dense deposits (P < 0.001). There were no significant differences in clinical features between the groups. Two children with SMGN underwent a repeat biopsy 3 yr after the first biopsy, and both patients again showed SMGN. At the final observation (mean observation time 7.5 yr in SMGN and 12.4 yr in GMGN), all children of both groups had a good outcome. In conclusion, these findings as a whole suggest that SMGN may be another glomerular disease entity with child predominance that is distinctive from GMGN.

Analysis of NPHS1, NPHS2, ACTN4, and WT1 in Japanese patients with congenital nephrotic syndrome.

BACKGROUND: Congenital nephrotic syndrome (CNS) causes significant renal failure, and is classified into two types: (1) Finnish type; and (2) other, including diffuse mesangial sclerosis. Mutations of NPHS1 and NPHS2, which encode the slit diaphragm components nephrin and podocin, cause CNS and autosomal-recessive familial steroid-resistant nephrotic syndrome, respectively. Most patients with Finnish-type CNS in Europe and the United States have NPHS1 mutations. However, NPHS2 mutations have been detected in some cases. Mutations in ACTN4, encoding alpha-actinin-4, cause an autosomal-dominant focal segmental glomerulosclerosis. alpha-actinin-4 stabilizes the podocyte cytoskeleton structure, connecting with actin filaments. WT1 mutations, causing Wilm's tumor, have been demonstrated in some CNS patients with diffuse mesangial sclerosis. Systematic investigation of genes for CNS in Japan has never been performed. METHODS: To clarify the role of mutations in these four genes, we used polymerase chain reaction (PCR) and direct sequencing to investigate all exons and exon-intron boundaries for these genes in 13 unrelated CNS patients from regional pediatric kidney disease centers in Japan. RESULTS: A novel homozygous nonsense mutation of NPHS1, E246X in exon 7, and a novel homozygous deletion mutation of NPHS1, 2156_2163del in exon 16 were detected in one patient each. A novel homozygous nonsense mutation of NPHS2, R196X in exon 5, was found in one patient, and the same heterozygous nonsense mutation was detected in another. No ACTN4 or WT1 mutations were detected. CONCLUSION: These studies demonstrate that mutation of NPHS1 is not a major cause of CNS in Japanese patients, and that mutation of NPHS2 can be responsible for CNS in this population.