Membranoproliferative glomerulonephritis associated with a mutation in Wilms' tumour suppressor gene 1

Focal Segmental Membranoproliferative Glomerulonephritis: A Histological Variant of Denys-Drash Syndrome

Introduction: Denys-Drash Syndrome (DDS) consists of a triad of pseudohermaphroditism, Wilms'tumor and nephropathy. This condition may manifest as a complete triad or in an incomplete form; with either one or a combination of the above features. The characteristic glomerular abnormality in DDS is diffuse mesangial sclerosis (DMS).Case report: We report two cases of DDS with focal membranoproliferative glomerulonephritis (MPGN). Both of our cases were males with ambiguous genitalia. They had a similar heterozygous germline mutation in exon 9 of WT1, c.1180C>T, p.R394W; a known mutation hotspot for DDS. Case 1 had nephropathy at the age of 4 years and Case 2 at 2.5 years with different rates of progression to end-stage renal failure. Conclusion: Our findings, in combination with other reports, illustrate the clinicopathological heterogeneity of DDS. There are no universal recommendations for optimal management of patients with DDS due to the inability to accurately predict affected individuals' progress.

Immune-complex glomerulonephritis with a membranoproliferative pattern in Frasier syndrome: a case report and review of the literature

Background

Mutations in the Wilms tumor 1 gene cause a spectrum of podocytopathy ranging from diffuse mesangial sclerosis to focal segmental glomerulosclerosis. In a considerable fraction of patients with Wilms tumor 1 mutations, the distinctive histology of immune-complex-type glomerulonephritis has been reported. However, the clinical relevance and etiologic mechanisms remain unknown.

Case presentation

A 5-year-old child presented with steroid-resistant nephrotic range proteinuria. Initial renal biopsy revealed predominant diffuse mesangial proliferation with a double-contour and coexisting milder changes of focal segmental glomerulosclerosis. Immunofluorescence and electron microscopy revealed a full-house-pattern deposition of immune complexes in the subendothelial and paramesangial areas. Serial biopsies at 6 and 8 years of age revealed that more remarkable changes of focal segmental glomerulosclerosis had developed on top of the initial proliferative glomerulonephritis. Identification of a de novo Wilms tumor 1 splice donor-site mutation in intron 9 (NM_024426.6:c.1447 + 4C > T) and 46,XY-gonadal dysgenesis led to the diagnosis of Frasier syndrome.

Conclusions

Our findings, together with those of others, point to the importance of heterogeneity in clinicopathological phenotypes caused by Wilms tumor 1 mutations and suggest that immune-complex-mediated membranoproliferative glomerulopathy should be considered as a histological variant.

Truncating Wilms Tumor Suppressor Gene 1 Mutation in an XX Female with Adult-Onset Focal Segmental Glomerulosclerosis and Streak Ovaries: A Case Report

About 30% of children with nephrotic syndrome (NS) have inherited forms. Among them, mutations in Wilms tumor suppressor gene 1 (WT1) are a well characterized cause associated with steroid-resistant NS, Wilms tumor, and urogenital malformation in males. However, the role of WT1 mutations in adult-onset focal segmental glomerulosclerosis (FSGS) is unclear. We report the case of a 38-year-old female with FSGS. She had been diagnosed with streak ovaries during diagnostic workup for infertility. Mutational analysis identified the heterozygous mutation c.1372C>T (p.Arg458*) in WT1 and the heterozygous non-neutral polymorphism c.868G>A (p.Arg229Gln) in NPHS2. Chromosomal analysis revealed a normal 46,XX female karyotype. Our case highlights that WT1 mutations should be considered in XX females with adult-onset FSGS, especially if urogenital abnormalities are present.

The podocyte as a target: cyclosporin A in the management of the nephrotic syndrome caused by WT1 mutations

Children with steroid-resistant nephrotic syndrome secondary to WT1-associated glomerulopathies (WT1-GP) were considered unresponsive to cyclosporin A (CsA). This assumption is challenged by the findings of recent studies. The patients of these studies had different types of WT1 mutations and varying clinical presentations. However, all of them were of young age and the favourable response to CsA might be the result of treatment at an early stage of the disease. The additional administration of angiotensin-converting enzyme inhibitors may have contributed to the positive outcome. We review recent data on the role of WT1 in the development of WT1-GP and discuss putative therapeutic targets explaining the therapeutic effect of CsA.

Recurrence of membranoproliferative glomerulonephritis after renal transplantation in Denys-Drash

Denys-Drash syndrome (DDS) consists of the triad of nephropathy, male pseudohermaphroditism, and Wilms tumor caused by mutations within exons 8 or 9 of the Wilms tumor suppressor gene 1. Early onset nephrotic syndrome progresses to end-stage renal failure. The characteristic histological lesion is diffuse mesangial sclerosis. Here, we report on a boy with DDS who presented early with diffuse mesangial sclerosis, but subsequently also developed immune complex glomerulonephritis with a membranoproliferative pattern (MPGN-pattern GN) in his native kidneys. Four years after renal transplantation, immune complex glomerulonephritis with an MPGN pattern recurred in the renal graft resulting in proteinuria and progressive renal insufficiency.

Successful treatment of steroid-resistant nephrotic syndrome associated with WT1 mutations

The Wilms' tumor suppressor gene 1 (WT1) encodes a transcription factor involved in kidney and gonadal development. WT1 is also a key regulator of podocyte functions and mutations have been found in a small percentage of children with isolated or syndromal steroid-resistant nephrotic syndrome. It is commonly assumed that the nephrotic syndrome (NS) in patients with WT1 mutations is unresponsive to therapy and characterized by rapid progression to end-stage renal disease. We report long-term observations in 3 children with focal-segmental glomerulosclerosis associated with WT1 mutations and NS (2 cases) or nephrotic range proteinuria (1 case). All patients showed a favorable response to an intensified therapy consisting of cyclosporin A (CyA) in combination with induction therapy with intravenous and oral prednisone. Treatment with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers was added to the regimen at various times. As shown both by the short-term response and during long-term follow-up, this treatment resulted in clinical remission of the NS and/or significant reduction of proteinuria, while normal renal function could be maintained over many years. Thus, glomerular diseases in selected patients with mutations in genes regulating renal development and podocyte function may respond to combination therapy with CyA and corticosteroids.

Genotype/phenotype correlation in nephrotic syndrome caused by WT1 mutations

BACKGROUND AND OBJECTIVES

The risk of developing Wilms tumor (WT) can be present or absent in patients with nephrotic syndrome (NS) caused by WT1 mutations. Here, the genotype/phenotype correlation regarding the outcome and risk for WT in 52 patients from 51 families with NS due to WT1 mutations is described.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study followed 19 patients with mutations in intron 9 splice donor site (KTS mutations), 27 patients with missense mutations, 4 patients with nonsense mutations, 1 patient with a splice site mutation in intron 8, and 1 patient with a deletion.

RESULTS

Twenty-four different WT1 mutations were detected. Sixteen of the 19 patients with KTS mutations were females. These patients had isolated NS if karyotype was 46,XX and Frasier syndrome if karyotype was 46,XY. Patients with KTS mutations presented at a significantly older age and with a slower progression toward chronic kidney disease (CKD) stage 5, compared with missense mutations. Patients with nonsense mutations presented initially with WT. Six patients with missense mutations developed WT after the diagnosis of NS (interval-range from NS onset to WT of 0.1 to 1.4 years).

CONCLUSIONS

(1) KTS mutations cause isolated NS with absence of WT in 46,XX females. (2) KTS mutations cause Frasier syndrome with gonadoblastoma risk in 46,XY phenotypic females. (3) KTS mutations cause NS with a slower progression when compared with missense mutations. (4) Missense mutations can occur with and without WT. (5) WT1 analysis is important in young patients with NS for early detection and tumor prophylaxis.