The Wilms Tumour gene 1 (WT1, NM_024426.6) holds significant importance in the developmental processes of the kidneys and gonads. Herein, we report a case of nephrotic syndrome and differences of sex development in a patient with novel mutations in WT1 gene. The child, identified as female based on social gender, exhibited symptoms at 6 years of age and was diagnosed with steroid-resistant nephrotic syndrome (SRNS). Renal biopsy findings indicated focal segmental glomerulosclerosis. Whole-exome sequencing unveiled a novel variant, c.1447 + 6(IVS9)T > C, in the WT1 gene, and karyotypic analysis revealed 46, XY, aligning with the phenotypic presentation of Frasier syndrome (FS, OMIM#136680) associated with WT1 gene mutation. The influence of gene variants on mRNA splicing was examined using in vitro minigene assays. The variant was classified as likely pathogenic (PS2 + PM2_Supporting + PP3) in accordance with American College of Medical Genetics and Genomics (ACMG) guidelines. in vitro minigene experiments demonstrated that the c.1447 + 6(IVS9)T > C variant altered the splicing pattern of exon 9 in the WT1 gene from two isoforms to a single form, thereby supporting its pathogenicity. Through high-throughput sequencing and in vitro minigene splicing experiments, the c.1447 + 6T > C variant in the WT1 gene was supported as the underlying genetic cause in the child patient, thereby expanding the spectrum of gene variants of WT1 gene and enhancing our comprehension of the molecular pathogenesis of this disorder.

In pediatric steroid-resistant nephrotic syndrome (SRNS), causative genetic abnormalities are now being identified. Immunosuppressive therapy is generally believed to be ineffective in treating Frasier syndrome, which is associated with genetic abnormalities. Recently, the efficacy of cyclosporine A (CyA) via a non-immunological mechanism has been reported. However, all of these reports have shown partial remission. In the present study, we report a case of nephrotic syndrome in a 1-year-old patient who was treated with CyA for SRNS. Complete remission was confirmed for 6 months, and the patient is currently in partial remission. Following confirmation of complete remission, hereditary nephrotic syndrome was not actively investigated; however, delayed secondary sexual characteristics' development led to the diagnosis of Frasier syndrome at the age of 13 years. Thus, immunosuppressive agents may have some efficacy in treating Frasier syndrome, particularly given that our patient achieved complete remission, indicating that it is worth considering administration of immunosuppressive agents for Frasier syndrome management.

WT1-related disorders comprise a spectrum of conditions resulting from mutations or deletions of the WT1 gene. Alteration in this gene have been associated with many syndromes, including WAGR syndrome, Denys-Drash syndrome (DDS), Frasier syndrome (FS) and Meacham syndrome. We present the case of an 8-year-old phenotypically female child with symptoms of end-stage kidney disease (ESKD), hypertension and anasarca, requiring renal replacement therapy. This case is distinctive due to its unusual onset, the presence of thrombotic microangiopathy (TMA), and the detection of a heterozygous missense mutation in the WT1 gene (c.1298G>A, p.Cys433Tyr) located in exon 8, in association with a 46 XY karyotype. The kidney biopsy indicated advanced focal segmental glomerulosclerosis (FSGS) with characteristics of TMA, implying a possible alternative diagnosis. In light of the heightened malignancy risk, the patient had preventative laparoscopic gonadectomy, which revealed rudimentary testicular tissues. The identified genotype points toward a diagnosis of DDS. However, the clinical presentation is more consistent with features typically seen in FS. This discrepancy highlights the significant phenotypic and genotypic overlap between the two syndromes. As a result, there is ongoing discussion in the literature about whether DDS and FS should be considered distinct clinical entities or rather variable expressions along a shared disease spectrum. WT1 disorder is characterized by congenital/infantile or childhood onset of steroid-resistant nephrotic syndrome (SRNS), a progressive glomerulopathy that does not respond to standard steroid therapy. Additional common findings can include disorders of testicular development (with or without abnormalities of the external genitalia and/or müllerian structures) and Wilms tumor. Less common findings are congenital anomalies of the kidney and urinary tract (CAKUT), gonadoblastoma, and 46,XX gonadal dysgenesis. In adulthood, most individuals are affected by early gonadal insufficiency of variable severity with potential impact on puberty and fertility. While various combinations of renal and other findings associated with a WT1 pathogenic variant were designated as certain syndromes in the past (the most common being Denys-Drash and Frasier syndromes), those designations are now recognized to be part of a phenotypic continuum and are no longer clinically helpful. The diagnosis of WT1 disorder is established in a proband with suggestive clinical findings and a heterozygous pathogenic variant in WT1 identified by molecular genetic testing. Treatment of manifestations: SRNS: avoid immunosuppressants; consider renin-angiotensin-aldosterone system (RAAS) inhibition. Disorders of testicular development and 46,XX gonadal dysgenesis: management is often by a multidisciplinary team (clinical geneticist, endocrinologist, urologist, and psychologist). Treat Wilms tumor with standard oncology protocols and, when applicable, nephron-sparing surgery. Treat CAKUT per standard care. Prevent whenever possible gonadoblastoma by prophylactic gonadectomy in those with a disorder of testicular development. Diaphragmatic hernia repair prior to the start of peritoneal dialysis. Surveillance: Monitor for first appearance of the following: proteinuria every six months until age ten years, yearly thereafter; Wilms tumor every three months until age seven years; early gonadal insufficiency yearly after puberty. For ongoing issues with disorders of testicular development and 46,XX gonadal dysgenesis, monitor per treating multidisciplinary team, and for CAKUT, monitor per treating nephrologist and/or urologist. Agents/circumstances to avoid: Avoid treating glomerulopathy with immunosuppressants, as they are not effective and potentially toxic. Evaluation of relatives at risk: It is appropriate to clarify the genetic status of apparently asymptomatic older and younger at-risk relatives of an individual with WT1 disorder in order to identify as early as possible those who would benefit from prompt initiation of treatment and surveillance for glomerulopathy and Wilms tumor. WT1 disorder is inherited in an autosomal dominant manner. Most individuals diagnosed with WT1 disorder have the disorder as the result of an apparent de novo WT1 pathogenic variant; in rare instances, a parent of an individual with WT1 disorder is heterozygous for the pathogenic variant identified in the proband. If a parent of the proband is affected and/or is known to have the WT1 pathogenic variant identified in the proband, the risk to the sibs of inheriting the pathogenic variant is 50%. If the WT1 pathogenic variant identified in the proband cannot be detected in the leukocyte DNA of either parent, the recurrence risk to sibs is slightly greater than that of the general population because of the possibility of parental gonadal mosaicism. Once the WT1 pathogenic variant has been identified in an affected family member, prenatal and preimplantation genetic testing are possible.

We present a case of a 19-year-old who developed nephrotic syndrome with preserved renal function. Renal biopsy confirmed focal segmental glomerular sclerosis (FSGS). No remission was achieved despite 2 years of treatment with glucocorticoids, mycophenolate mofetil, tacrolimus, and cyclophosphamide. After transfer to our center, we performed re-examination of renal pathology by electron microscope (EM), chromosomal karyotype, and gene analysis. EM revealed uneven thickness of the glomerular basement membrane without obvious stratification or fracture. Gene analysis revealed a splice mutation (1447+1G>A) in IVS9 and chromosomal karyotype was (46, XY), confirming the diagnosis of Frasier syndrome, which was consistent with primary amenorrhea overlooked by local nephrologists. Cyclosporin A was prescribed to reduce the proteinuria, but serum creatinine increased to 152 μmol/L.

The Wilms tumor 1 (WT1) gene was first identified in 1990 as a strong candidate for conferring a predisposition to Wilms tumor. The WT1 protein has four zinc finger structures (DNA binding domain) at the C-terminus, which bind to transcriptional regulatory sequences on DNA, and acts as a transcription factor. WT1 is expressed during kidney development and regulates differentiation, and is also expressed in glomerular epithelial cells after birth to maintain the structure of podocytes. WT1-related disorders are a group of conditions associated with an aberrant or absent copy of the WT1 gene. This group of conditions encompasses a wide phenotypic spectrum that includes Denys-Drash syndrome (DDS), Frasier syndrome (FS), Wilms-aniridia-genitourinary-mental retardation syndrome, and isolated manifestations of nephropathy or Wilms tumor. The genotype-phenotype correlation is becoming clearer: patients with missense variants in DNA binding sites including C2H2 sites manifest DDS and develop early-onset and rapidly developing end-stage kidney disease. A deeper understanding of the genotype-phenotype correlation has also been obtained in DDS, but no such correlation has been observed in FS. The incidence of Wilms tumor is higher in patients with DDS and exon-truncating variants than in those with non-truncating variants. Here, we briefly describe the genetic background of this highly complicated WT1-related disorders.