Wilms tumor suppressor gene-1 (WT1) mutations are associated with life-threatening nephropathy including congenital or/ infantile nephrotic syndrome (CNS) and/or childhood onset steroid-resistant nephrotic syndrome (SRNS) as well as a spectrum of disorders of sexual development (DSD), Wilm's tumor and gonadal malignancies. SRNS is one of the most common causes of end-stage kidney disease (ESKD) in children and adolescents with up to 25% of cases associated with a genetic abnormality preferentially expressed in the podocytes (1, 2). Traditional syndromic terminology includes the terms of Denys-Drash Syndrome, which represents early-onset nephrotic syndrome, Wilm's tumor, and male pseudo-hermaphroditism as well as Frasier Syndrome with late-onset SRNS and gonadal dysgenesis.

The WT1 gene is localized on chromosome 11p13 and encodes a transcriptional factor of the zinc-finger protein family. The advances in genetic diagnostic tests have increased the ability to identify genetic causes of childhood SRNS. The WT1 gene is a tumor suppressor gene necessary for the development of the kidney and gonads. In the fetal kidney, WT1 protein is highly expressed in the areas of active glomerulogenesis, which supports a major role of the gene in the development and maturation of the glomerular filtration barrier (2). Germline heterozygous WT1 mutations are known to manifest as the developmental genital abnormalities including 46XY sex reversal with complete female phenotype and various anomalies of the male genitalia such as cryptorchidism and hypogonadism (3, 4). In the recent years, the consensus has been to move away from these terms since the spectra of clinical and phenotypic diseases overlap (5). The risk of Wilm's tumor and gonadoblastoma in individuals with WT1 mutations is ominous and merits close surveillance for yet an undetermined period. Therefore, early recognition of WT1 mutation is critical for the early detection of neoplasia and counseling regarding sexual development and reproductive health. A number of international studies have described the incidence and prevalence of this rare disease and case reports, with comprehensive reviews on the clinical manifestations of WT1 gene mutations in the pediatric population (6–10).

Our objectives through this case series and contemporary literature review were to describe the clinical presentation, which includes extra-renal manifestations, age of diagnosis, progression, and complications of WT1 glomerulopathy. We also sought to develop a paradigm for earlier recognition and genetic diagnosis through the phenotypic correlations.

A retrospective chart review of patients followed at the University of Miami/Holtz Children's Hospital from January 2000 to December 2020 with a diagnosis of WT1 gene mutation was performed. Data collection that included age at presentation, sex, ethnicity, karyotype, initial presentations of kidney and extrarenal disease, age at diagnosis of WT1 mutation, at ESKD, and at transplantation as well as complications related to WT1 mutation that includes malignancy and gonadal disorders was recorded.

A comprehensive literature search and review for original articles and case reports with WT1 mutation and glomerulopathy published from 2000 to August 2021 was performed through PubMed. The core concept was to identify information on the spectrum of clinical manifestations and diagnosis of WT1 mutation. More specifically, sex, karyotype, and significant complications that include type of malignancy were extracted when available. The two authors independently performed the literature search using keywords: WT1 mutation, Denys-Drash, Frasier, genotype, CNS, SRNS, glomerulopathy, or nephropathy. The abstracts of all selected articles were reviewed, and references from retrieved articles were used to identify other relevant sources. To make data extraction accurate and consistent, the studies that did not specify clinical manifestations or karyotype were excluded. Only articles in the English language were reviewed.

This study was approved by the institutional review board of the University of Miami with the waiver of informed consent and protection of privacy in compliance with the Health Insurance Portability and Accountability Act (HIPAA).

With this case series and extensive literature review, we have compiled important clinical, sex, and karyotype characteristics and projected long-term outcomes of 333 cases with an estimated 500 cases reported worldwide since it was first described in 1991 (5, 40). Although considered an extremely rare disease (41), the broad spectrum of clinical manifestations has become more apparent, and it is suspected that many cases may go unrecognized (8, 27, 42, 43).

Proteinuria is the most frequent and pervasive manifestation of the WT1 mutation from birth through childhood to adulthood (5, 8, 42, 43). It occurred in 92% of the 333 cases at presentation in our current review, which is consistent with the previous reviews (8, 42, 43). The progression to ESKD is also synchronous with proteinuria. The concurrence of CNS with renal failure is a frequent clinical presentation in infancy, whereas SRNS with slower progression to ESKD occurs later in childhood.

In this case series and literature review, we were unable to refine the clinical phenotypes with the specific WT1 mutation analyses which have become more available in the recent years. These studies have been able to categorize the various mutations with broader clinicopathologic correlations (39). Over 30 mutations or missense variants of the WT1 protein have been analyzed, reported, and correlated with phenotypes that include proteinuria, ESKD, genital anomalies, and Wilm's tumor (13). Subjects with exon 6-9 WT1 missense mutations display partial gonadal dysgenesis and late-onset nephropathy. The intron 9 splice-site mutations with the 3 amino acid residues–lysine (K), threonine (T), and serine (S)–referred to as the +KTS is an important element in gonadal development and the WT1 variant that affects the +KTS/-KTS ratio of the isoforms to <2.0 results in abnormal gonadal development with sexual reversal (female XY-DSD) phenotype and late-onset nephropathy. Importantly, the XY sex reversal with female phenotype appears to be protective against the development of Wilm's tumor while it is associated with high risk for gonadoblastoma (19, 44, 45). Although rare, there were 2 cases of Wilm's tumor with female XY sex reversal in this case series (7, 8).

Malignancy is the most ominous complication of the WT1 mutation and its occurrence relative to the clinical phenotypic–genotypic profile was delineated by the analysis of the 333 cases in our review. Importantly, Wilm's tumor with WT1 mutation tends to occur early with a median age of 15–19 months vs. a median age of 36 months in children without a pathogenic WT1 variant (5). Any early-onset Wilm's tumor or bilateral Wilm's tumor should have WT1 mutation analysis. The 20-year registry of Wilm's tumor has shown that 1.3% of those with unilateral and 15% with bilateral Wilm's tumor progressed to ESKD (46). Hence, this mutation should be considered in toddlers, as well as in cases of bilateral Wilm's tumor (5). A recent single center retrospective analysis of 25 long-term Wilm's tumor survivors with WT1 pathogenic variants confirmed male predominance (60%), early age occurrence (median 14 months), multiple genetic variants, high incidence of bilateral disease (52%), and genitourinary malformations (44%) (47). This recent report emphasized the importance of early genetic diagnosis to better inform surgical management toward the preservation of renal mass when oncologic management is not compromised. Importantly, our report is the first to describe long-term outcomes of those with WT1 mutations post-transplantation. It is notable that we report a cumulative of over 170 patient years with no evidence of post-transplant malignancy.

The complete sex reversal with 46 XY female phenotype is associated with late-onset SRNS, and CKD has been typically categorized as “Frasier syndrome.” These patients are often not diagnosed until adolescence when they fail to achieve puberty. Importantly, this unique phenotype is associated with the KTS gene variant that seems to impart “protection” against the development of Wilm's tumor. It does not prevent gonadoblastoma because the gonads are dysplastic. As in our series, 2 phenotypic females presented with CNS and childhood SRNS, but they were not diagnosed with WT1 mutation until adolescence when a karyotype was obtained as workup for delayed puberty. These are examples of the wide spectrum of clinical presentations and progression of disease that make the designations of Denys-Drash and Frasier syndromes indistinct. This contributes to the paradigm that calls for the genetic investigation including karyotype of any phenotypic female who presents with CNS, SRNS or proteinuria, or ESKD concerning for possible 46XY sex reversal associated with WT1 glomerulopathy. The fact that the XY karyotype predominates in most series suggests that we are probably missing the diagnosis in a number of females, especially those with familial proteinuria (5, 8, 42, 43).

The risk of malignancy associated with WT1 mutation compels the discussion of whether prophylactic nephrectomy and/or gonadectomy should be considered once the diagnosis is confirmed. In the context of this study and others in the literature review, the characterization of the risks of malignancy according to phenotype–karyotype is extremely pertinent (14, 48, 49). Importantly, the current analysis of 333 cases shows that normal male XY phenotype–karyotype is at low risk for any malignancy. However, normal female XX phenotype–karyotype has very low risk for gonadoblastoma but remains at risk for Wilm's tumor, especially in early life. Historically, there has been an unsubstantiated concession to perform prophylactic nephrectomies in young children with WT1 mutation, especially in the setting of prior Wilm's tumor or in preparation for transplantation (48). Currently, there is no consensus for prophylactic nephrectomies. In the literature review, there were no specific recommendations in favor of prophylactic bilateral nephrectomy, and most recently, the recommendation has been for renal sparing surgery in the case of unilateral Wilm's tumor (14, 47–49). In marked contrast, there is a strong consensus for prophylactic gonadectomy in all phenotypic females with 46 XY sex reversal. Moreover, our results show the increased risk of malignancy in phenotypic males with DSD and emphasize the need for close surveillance and a low threshold for prophylactic gonadectomy (47–50).

Comprehensive data on the surgical and medical management of sexual health in children with WT1 mutations are lacking. There is a need to better understand hormonal replacement, erectile dysfunction, cosmesis for urogenital abnormalities, and reproductive capacity. Endocrine data are scarce in subjects with WT1 mutations. Long-term follow-up with the development of novel markers to evaluate and predict gonadal malignancies is imperative.

We propose a paradigm designed to initiate early comprehensive genetic testing followed by clinical surveillance (Figure 4). The goals are for (1) early phenotypic recognition leading to genomic diagnosis; (2) appropriate surveillance for progression to CKD, malignancy, and sexual health in patients with WT1 mutations; (3) genetic analysis to precede kidney biopsy in children with SRNS; (4) establish early medical management to modulate proteinuria and preserve long-term kidney function; (5) genetic counseling for the patient and family related to fertility and future pregnancies; and (6) expansion of the knowledge database by collaboration and reporting of new cases. Current recommendations include early genomic analyses by next generation sequencing (NGS) and karyotyping of any infants (< 1 year of age) with proteinuria including CNS, SRNS, and/or male DSD (51).

This study has several limitations including those inherent in extracting accurate detailed case characteristics from an in-depth literature review. There may have been publication bias from distinct case reports, particularly involving malignancy or karyotype–phenotype correlations. This is especially true in the case of XY-karyotype with severe gonadal dysmorphia and ambiguous phenotype. Nevertheless, the impact of WT1 mutations and the long-term consequences on patient's health merits comprehensive and contemporary review to promote early recognition and genetic screening.

Early recognition of WT1 gene mutation is essential for appropriate medical and surgical management. This includes the use of renal preservation therapy to modulate proteinuria and hyperfiltration with angiotensin blockade, avoidance of immunosuppressive treatment before kidney transplantation, surveillance, and early detection of malignancy. Further, these patients would benefit from multi-disciplinary care from primary care providers, nephrologists, endocrinologists, urologists, and psychologists to establish appropriate long-term management of psychosocial and sexual health. In this case series, kidney transplantation has provided long-term patient and allograft survival with no increased incidence of malignancy post-transplant.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

The studies involving human participants were reviewed and approved by University of Miami Institution Review Board. Written informed consent from the participants' legal guardian/next of kin was not required to participate in this study in accordance with the national legislation and the institutional requirements.

PA-P, WS, and CA wrote the first draft of the manuscript. WS, CK, MD, and CA participated in the critical analysis of the data and the major revisions of the manuscript. All authors contributed to the conception, design of the study, contributed to manuscript revision, read, and approved the final version of the manuscript.

This work was supported in part by the Lilian Barbarosh Pediatric Renal Research Fund.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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