Gonadal Tumor in Frasier Syndrome: A Review and Classification

Frasier syndrome and Denys–Drash syndrome (DDS) are both rare inherited diseases characterized by steroid-resistant nephrotic syndrome, which leads to renal failure, gonadal tumor (most commonly gonadoblastoma or dysgerminoma), and male pseudohermaphroditism (female external genitalia with sex chromosomes XY; ref. 1). In comparison with other conditions in which male pseudohermaphroditism is present, the risk of gonadal tumor is particularly high in Frasier syndrome (60% compared with 40% for DDS and 15% for partial androgen insensitivity syndrome; ref. 2). Early diagnosis and early elective bilateral gonadectomy have, therefore, been recommended for patients with Frasier syndrome and DDS (3, 4).

Frasier syndrome and DDS are both caused by specific mutations in the Wilms tumor-suppressor gene (WT1), which is located in autosome 11p13 (3). In DDS, a dominant negative mutation in exons 8 or 9 of WT1 leads to the production of abnormal WT1 protein, which results in renal failure before 1 year of age and the development of Wilms tumor of the kidney (1). In contrast, in Frasier syndrome, a point mutation on the donor splice site on intron 9 [intervining sequence (IVS 9)] of WT1 leads to a slow progression of glomerulopathy, leading to proteinuria and nephrotic syndrome in childhood, followed by renal failure in adolescence or early adulthood. Only one case of Frasier syndrome associated with Wilms tumor has been reported (5). The presence of focal segmental glomerulosclerosis or diffuse mesangial sclerosis limits the utility of renal histopathology in distinguishing between these two syndromes (6).

WT1 is a regulator of early gonadal and renal development (7). Two major WT1 isoforms are produced by alternative splicing of the lysine–threonine–serine (KTS) domain, including an insertion (+KTS) or deletion (−KTS; ref. 3). The +KTS isoform of WT1 participates in RNA processing, and has been shown to play a crucial role in the regulation of sex-determining region Y (SRY) in vivo in mice (3, 7). Thus, it can be surmised that WT1 or SRY mutations can induce early errors in the processes of sex determination mediated by preventing proper formation of the testis. Furthermore, sex reversal is observed in male mice deficient in the +KTS isoform of WT1 (7). In human patients with Frasier syndrome, a point mutation on IVS9 brings about downregulation of the +KTS isoform of WT1, which in turn diminishes SRY expression levels (8), and thereby impairs testicular development (7). Thus, male to female sex reversal will occur in pediatric Frasier syndrome patients with 46,XY (9).

Because most patients with Frasier syndrome have external female genitalia and are raised as girls, Frasier syndrome is often suspected when these children with steroid-resistant nephrotic syndrome are evaluated for delayed puberty or primary amenorrhea. The diagnosis is confirmed by detecting WT1 mutations (3). Because of the high risk of gonadal tumor, early diagnosis of Frasier syndrome and early gonadectomy are very important for preventing tumorigenesis (3, 4). However, because most Frasier syndrome patients only present with slowly progressing renal failure, it is very difficult to distinguish it from primary amenorrhea associated with other disorders. A possible option for early diagnosis of Frasier syndrome might be the genetic screening of children with steroid-resistant nephrotic syndrome.

Over the past two decades, several cases of Frasier syndrome of unusual phenotype have been reported. These cases carry a Frasier syndrome–specific IVS 9 mutation in WT1 without the presence of male pseudohermaphroditism. These cases can be classified into two types: patients with male chromosomes (XY) and male external genitalia, and patients with female chromosomes (XX) and female external genitalia. Mother and daughter cases of Frasier syndrome with transmission of WT1 splice-site mutation have been reported (10). The clinical features of these “unusual” cases differ from classical Frasier syndrome.

Previous review articles concerning Frasier syndrome have not provided detailed descriptions of the clinical features and treatment of classical and unusual cases (7, 11). Here, we review the literature, focusing on clinical course, mutation patterns, and prevalence rates of gonadal tumor in classical and unusual cases of Frasier syndrome. We also propose a new classification system for Frasier syndrome, which may be applied to genetic diagnosis and therapeutic strategies.

A systematic search of the MEDLINE database up to February 2014 was performed to identify literature with the search term, “Frasier syndrome.” In addition, an extensive manual search was conducted using references from all retrieved reports and review articles. Initially, we found 99 cases that were classified as Frasier syndrome. However, for the purpose of the current analysis, 8 cases were excluded because they lacked descriptions about external genitalia and/or karyotype. Two cases with WT1 mutations (1168C→T and 1174T→C) in exon 9 but not IVS 9 mutation have been reported as unusual Frasier syndrome (12). Although these mutations are also consistent with DDS, both slow progression of steroid-resistant nephrotic syndrome and the absence of Wilms tumor indicate Frasier syndrome (12). However, the fact that these cases were not associated with abnormal KTS splice isoforms suggests an etiology similar to DDS rather than Frasier syndrome. We therefore excluded these two cases from our study. Another unusual Frasier syndrome case showed external genitalia of female phenotype, chronic renal failure, and primary hypogonadism as well as defects of the uterine cervix, body and tubes, and gonads on pelvic MRI (13, 14). However, the case was excluded from our study because genetic analysis of WT1 was not performed. The inclusion criteria for our review of the Frasier syndrome literature were as follows: (i) the presence of steroid-resistant nephrotic syndrome; and (ii) the presence of male pseudohermaphroditism or IVS 9 mutation. In total, 88 Frasier syndrome cases were selected for our review (Supplementary Table S1).

Because Frasier syndrome is caused by a point mutation in the IVS9 of WT1 located on chromosome 11 (autosome), by which abnormal WT1 + KTS protein are produced (7), both males and females can suffer from Frasier syndrome. However, the interaction between SRY and abnormal WT1 + KTS protein means that the presence of SRY (male) affects phenotype in Frasier syndrome. Moreover, it is hypothesized that there is a gene on the Y chromosome that is involved in the development of gonadoblastoma (15). This is called the gene for testis-specific protein Y (TSPY), which has been referred to as the gonadoblastoma locus on the Y chromosome (GBY; ref. 16). However, the complete mechanism by which the TSPY product causes tumorigenesis remains to be elucidated (2). Therefore, we classified Frasier syndrome from viewpoints such as sex chromosome and external genitalia.

All of the selected cases were categorized into three types: type 1 cases with female external genitalia and 46,XY (n = 72); type 2 with male external genitalia and 46,XY (n = 8); and type 3 cases with female external genitalia and 46,XX (n = 8; Table 1). To our knowledge, there have been no cases of Frasier syndrome with male external genitalia and 46,XX.

We extracted information on the “first complaint” and the “complaint that lead to diagnosis of Frasier syndrome” from each of the 88 cases, and compared their clinical course. Proteinuria, nephrotic syndrome, and hypertension, or edema due to renal failure were abbreviated as “renal disorder,” and primary amenorrhea and/or delayed puberty were abbreviated as “delayed secondary sex characteristics.” The number of cases, age of complaints, types of WT1 mutation and histopathologic type of gonadal tumor were described for each type of Frasier syndrome (Table 1). We diagnosed a case with coexisting gonadoblastoma and dysgerminoma as having dysgerminoma, which is more malignant than gonadoblastoma.

To elucidate the characteristics of gonadal tumor in type 1, we compared the age at gonadectomy and between three groups: cases without gonadal tumor, cases with gonadoblastoma and cases with dysgerminoma (Table 2). To explore the relationship between the types of WT1 mutation and the occurrence of gonadal tumor, we also compared the difference in the number of cases corresponding to each type of WT1 mutation (Table 2).

Age was expressed as mean ± SD. One-way ANOVA was used for continuous variables, and the χ² test was used for categorical variables. Statistical analyses were performed using the SPSS statistics software, version 20 (IBM). A P value of <0.05 was considered to be statistically significant.

The majority of cases reported in the literature (n = 72, 82%) were of type 1 Frasier syndrome (Table 1). In type 1, the most common “first complaint” (that which prompted parents of Frasier syndrome patients to first visit a clinic), was renal disorder in the infant period (n = 49, mean age at first visit: 5.4 ± 4.3 years). Only seven type 1 cases were diagnosed with Frasier syndrome at this point. Most other type 1 patients were diagnosed in adolescence due to delayed secondary sexual characteristics (n = 36, mean age at diagnosis: 16.3 ± 2.3 years). In the cases with descriptions of WT1 mutation, 90% of genetic mutations were restricted to IVS9 +4 and IVS9 +5 of WT1.

The characteristics of gonadal tumor (n = 45) in type 1 Frasier syndrome are summarized in Table 2. A previous study indicated that early diagnosis of Frasier syndrome and early gonadectomy prevented the occurrence of gonadal tumor (4). To verify this association, we compared the mean age at gonadectomy in cases without gonadal tumor, cases with gonadoblastoma, and cases with dysgerminoma. The tendency for cases with clinically aggressive gonadal tumor phenotypes to undergo early gonadectomy creates a reverse causal problem. We therefore conducted analyses separately: cases noticed because of renal disorder or delayed secondary sexual characteristics and cases noticed because of abdominal pain or mass. There was no statistically significant difference of age at gonadectomy and position of WT1 mutation among the three groups: cases without gonadal tumor, cases with gonadoblastoma and cases with dysgerminoma (P = 0.519 for age at gonadectomy and P = 0.779 for position of WT1 mutation, Table 2). Neoplastic transformations seem to occur in the period of adolescence. However, our study's cross-sectional design meant that we could not ascertain the rate of gonadal tumor occurrence.

Six Frasier syndrome cases were diagnosed by the presence of abdominal pain or mass, all of which had gonadal tumor [gonadoblastoma (refs. 17–19), or dysgerminoma (refs. 20–22)]. In some cases, metastasis (17), or recurrence (20) was observed. These cases underwent gonadectomy around the age of 11, which was earlier than in cases diagnosed by the presence of renal disorder and/or delayed secondary sexual characteristics. Among the 46,XY Frasier syndrome cases, 32 (67%) had gonadal tumor, suggesting that the risk of gonadal tumor is higher than that reported in previous studies [60%; (ref. 11) and 48% (ref. 7)].

Eight cases of type 2 Frasier syndrome have been reported (8, 12, 23–29). Although 5 of the cases initially visited clinics due to hypospadia or aplasia of testis (mean age at first visit: 1.0 ± 2.2 years), in most cases, these features did not lead to the diagnosis of Frasier syndrome. Three cases were diagnosed during investigation of renal disorder, and four cases were diagnosed because of other features (Table 1). Features that lead to the diagnosis of Frasier syndrome in these four cases include testicular nodule (gonadoblastoma; ref. 27), genetic investigation due to familial history of Frasier syndrome (28, 29), and severe hypertension due to renal failure (24).

Interestingly, both the distribution and pattern of WT1 mutation in type 2 Frasier syndrome were different from those in type 1 Frasier syndrome. The number of patients with IVS9 +5G→A (n = 27) was larger than patients with IVS9 +4C→T (n = 17) in type 1 Frasier syndrome, whereas the number of patients with IVS9 +5G→A (n = 2) was smaller than patients with IVS9 +4C→T (n = 5) in type 2 Frasier syndrome (P = 0.11 for the χ² test of IVS9 +4C→T and IVS9 +5G→A; Table 1). The position of the altered base could influence the ratio of +KTS and −KTS isoforms of WT1 protein, by which external genitals were determined. However, it is also conceivable that other mutations may affect the phenotype of external genitalia. Whole-genome sequencing in types 1 and 2 Frasier syndrome patients may clarify the mechanism by which external genital phenotypes are determined.

Among the 8 cases of type 2 Frasier syndrome, three cases first presented because of gonadal tumors: Sertoli cell tumor and seminoma (23), intratubular germ cell neoplasia unclassified (ITGCN; ref. 8), and gonadoblastoma (27). There is no description concerning gonadectomy in cases without gonadal tumor (24, 26, 28–30). The rate of gonadal tumor in type 2 Frasier syndrome cases remains unclear. Because type 2 Frasier syndrome cases do not present primary amenorrhea, the presence of steroid-resistant nephrotic syndrome in children with male external genitalia may provide a chance to examine mutations in WT1. Clinicians should pay attention to the history of infantile hypospadias or aplasia of testis.

Eight cases of type 3 Frasier syndrome have been reported (10, 13, 14, 31–36). Few type 3 Frasier syndrome cases are diagnosed because patients exhibit normal secondary sexual characteristics by the XX chromosome and suffer from renal failure without gonadal impairment. In a previous case report on mother-to-child transmitted WT1 splice-site mutation (10), the mother (46,XX) had an IVS9+5G→A mutation of WT1 and renal failure without gonadal impairment, and her 46,XY daughter had the same mutation and renal failure. It is of interest that the mother and daughter seem to be of types 3 and 1, respectively. These cases point to the possibility that a 46,XY child who is born to a type 3 Frasier syndrome parent could have type 1 Frasier syndrome. In this regard, WT1 sequencing is useful not only in instances of sporadic steroid-resistant nephrotic syndrome, but also in familial cases. Thus, it should be considered with caveat that patients with type 3 Frasier syndrome, as well as those with types 1 and 2, might require careful genetic counseling.

It is noteworthy that there were no cases of type 3 Frasier syndrome with gonadal tumor (Table 1). The absence of gonadal tumor in type 3 Frasier syndrome, in contrast with the other types, suggests the possibility that a gonadoblastoma-related gene locus exists on the Y chromosome (15). On the basis of this finding, it would seem that gonadectomy should not be recommended in cases of type 3 Frasier syndrome. However, the existence of 8 non–Frasier syndrome cases with gonadoblastoma in pure 46,XX females suggests that there is a level of risk of gonadal tumor in type 3 Frasier syndrome that cannot be ignored (37, 38). The prudent recommendation in type 3 Frasier syndrome cases might, therefore, be that medical practitioners carry out careful follow-up examinations of gonadal (ovarian) tissues.

On the basis of the results of our review of 88 Frasier syndrome cases, we classified Frasier syndrome into three types (types 1–3 Frasier syndrome). All genetic mutations were detected at the IVS9 region of WT1. However, the rates of occurrence of gonadal tumor and clinical features differed among the three types. Although gonadal tumor was frequently present in types 1 and 2, it was not present in any type 3 Frasier syndrome cases. In comparison with other studies, our study showed a higher risk of gonadal tumor (67%) in type 1 Frasier syndrome (7, 11). Six cases were diagnosed in response to abdominal pain or mass reflecting gonadal tumor (17–22), of which two showed metastasis or recurrence (17, 20). These six cases underwent gonadectomy at around 11 years of age—which was younger than in cases diagnosed in response to renal disorder, delayed secondary sexual characteristics, or both. These data suggest that diagnosis of Frasier syndrome before puberty requires sequencing analysis of WT1. Gonadal tumor is also a risk in type 2 Frasier syndrome cases. Thus, early diagnosis and early gonadectomy should be considered in cases of types 1 and 2. However, given that no cases of gonadal tumor have been reported from type 3 Frasier syndrome, gonadectomy should not be recommended in type 3—even if that necessitates the further follow-up examination of gonadal tissues.

A large number of genetic mutations have been identified in subjects with steroid-resistant nephrotic syndrome and focal segmental glomerulosclerosis. A genetic testing algorithm for steroid-resistant nephrotic syndrome based on age at onset and familial/sporadic status was recently reported (39). According to the algorithm for infantile and child onset steroid-resistant nephrotic syndrome, WT1 gene analysis should be performed only in patients with “sporadic steroid-resistant nephrotic syndrome” and “female external genitalia” who are negative for mutation in the gene for nephrosis 2, idiopathic, and steroid-resistant (podocin; NPHS2). NPHS2 mutation is the most common cause of infantile and child onset steroid-resistant nephrotic syndrome (39).

Cases of Frasier syndrome types 2 and 3 show steroid-resistant nephrotic syndrome but not primary amenorrhea. Although there is a lack detailed data concerning age of onset, the age at onset of renal disorder represented by proteinuria ranges from 1 to 18 years. In other words, these data point to the possibility that cases of steroid-resistant nephrotic syndrome in patients of 1 to 18 years of age could include cases of type 2 and 3 Frasier syndrome. The fact that there are Frasier syndrome cases displaying male external genitalia (type 2 Frasier syndrome according to our classification) or suspected familial steroid-resistant nephrotic syndrome (10), indicates that it is noteworthy to consider sequencing analysis of WT1 not only in patients with female external genitalia and sporadic steroid-resistant nephrotic syndrome, but also in those with male external genitalia or familial steroid-resistant nephrotic syndrome. Regarding these characteristics, we have proposed a new diagnostic algorithm for Frasier syndrome (Fig. 1).

Taken together, we summarized and reviewed the clinical, genetic, and pathologic features of 88 Frasier syndrome cases. It is very important to perform early diagnosis and type classification on Frasier syndrome cases. Further investigations using epidemiologic, genetic, and molecular biologic approaches will be addressed to verify the ultimate significance of our new classification system, which is linked to clarifying the etiology of Frasier syndrome and therapeutic strategies.

No potential conflicts of interest were disclosed.