[Swyer syndrome with gonadal non-dysgerminoma malignant germ cell tumors: a report of 15 cases in a national medical center].

Objective: To evaluate the incidence, treatment, and survival outcomes of Swyer syndrome with gonadal non-dysgerminoma malignant germ cell tumor (MGCT-NDG). Methods: A retrospective study was performed on Swyer syndrome patients with MGCT-NDG between January 2011 and December 2022 in Peking Union Medical College Hospital to investigate their characteristics and outcomes. Results: A total of 15 patients (4.9%, 15/307) with Swyer syndrome were identified in 307 MGCT-NDG patients. The average age at diagnosis of MGCT-NDG and Swyer syndrome were (16.8±6.7) and (16.7±6.6) years, respectively. Six cases were preoperatively diagnosed as Swyer syndrome, of which 4 cases received bilateral gonadectomy with or without hysterectomy, while the other 2 cases underwent removal of gonadal tumor and unilateral gonadectomy with hysterectomy, respectively. Of the 9 patients postoperatively diagnosed as Swyer syndrome, unilateral gonadectomy, removal of gonadal tumor, and unilateral gonadectomy with hysterectomy were performed in 6 patients, 2 patients, and 1 patient, respectively. Mixed malignant germ cell tumor (MGCT;10 cases), yolk sac tumor (4 cases), and immature teratoma (1 case) were the pathological subtypes, in the descending order. There were International Federation of Gynecology and Obstetrics (FIGO) stage Ⅰ in 6 cases, stage Ⅱ in 3 cases, stage Ⅲ in 5 cases, and stage Ⅳ in 1 case, respectively. Eleven patients received reoperation for residual gonadectomy after a average delay of (7.9±6.2) months, including 8 MGCT-NDG patients and 1 gonadoblastoma patient, no tumor involved was seen in the remaining gonads in the other 2 cases. Ten patients experienced at least one recurrence, with a median event free survival of 9 months (5, 30 months), of which 2 patients received surgery only at the time of initial treatment. All patients with recurrence received surgery and combined with postoperative chemotherapy. After a median follow-up of 25 months (15, 42 months), 10 patients were disease-free, 3 patients died of the tumor, 1 died of side effects of leukemia chemotherapy, and 1 survived with disease. Conclusion: The incidence rate of Swyer syndrome in patients with MGCT-NDG is about 4.9%; timely diagnosis and bilateral gonadectomy should be emphasized to reduce the risk of reoperation and second carcinogenesis in this population.

Acute Lymphoblastic Leukemia Developing in a Patient with 46, XY Pure Gonadal Dysgenesis (Swyer Syndrome) with Malignant Gonadal Germ Cell Tumor: A Case Report and Literature Review.

A female phenotype with strip-like gonads, 46, XY pure gonadal dysgenesis (PGD) has a high tendency to develop into gonadal germ cell tumors. We described one patient with 46, XY PGD, who had a gonadal mixed germ cell tumor (GCT) and acute lymphoblastic leukemia (ALL). This is a unique case because two malignancies developed and relapsed in one person with chromosome abnormality, and the patient is the youngest reported so far. There is an association between her GCT and ALL, as the two malignancies may share a common clonal origin and the NRAS mutation likely plays a role in tumor genesis. We organized MDT to formulate a suitable plan of treatment. We completed the surgery and full cycles of chemotherapy for GCT and controlled ALL by chemotherapy and bone marrow transplantation. However, unfortunately, the young life finally ended following a rare transplant rejection. We concluded that ALL likely shares common clonal origin with GCT and that gene mutations may play a role in neoplasia, which requires further exploration. In the face of such complex conditions, we need to balance the treatment of both diseases to prolong survival and improve the patients' quality of life.

Non-obvious diagnosis and breast development in pure gonadal dysgenesis.

Pure gonadal dysgenesis is a situation when the karyotype is 46, XY, but for various reasons there is a disorder of differentiation of Wolffian and Mullerian structures and in consequence the phenotype is female. It is known that abdominal gonads and the presence of Y chromosome allow to qualify this condition as a high risk of tumor. In most cases breast development is limited because of lack or low level of estrogen. A 27-year-old patient with differences of sexual development (DSD), was admitted to the Department of Endocrinological Gynecology for a control examination. In the history: dysgerminoma, primary amenorrhea and ambiguous karyotype. The patient has not taken hormonal replacement therapy. The breast development is Tanner stage V.

46, XY complete gonadal dysgenesis with pubertal virilisation due to dysgerminoma/gonadoblastoma.

Complete gonadal dysgenesis (CGD) or Swyer syndrome is characterised by sexual infantilism in a phenotypic female with 46, XY karyotype. Patients with gonadal dysgenesis and Y-chromosome material are at a high risk of developing gonadoblastoma and dysgerminoma. A 16-year-old girl presented with progressive virilisation, poor breast development and primary amenorrhea. On evaluation, she was found to have male-range serum testosterone, large abdominopelvic mass lesion, elevated germ cell tumour markers and 46, XY karyotype. She underwent surgical excision of left gonadal mass and right streak gonad, histopathology of which revealed dysgerminoma and gonadoblastoma, respectively. A diagnosis of virilising germ cell tumour arising in the setting of 46, XY CGD was, therefore, made. This case highlights a rare presentation of 46, XY CGD and the need to consider early prophylactic gonadectomy in patients affected with this rare condition. The presence of dysgerminoma/gonadoblastoma should be suspected if a hitherto phenotypic female with CGD undergoes virilisation.

Monochorionic diamniotic twins of discordant external genitalia with 45,X/46,XY mosaicism.

BACKGROUND: Monozygotic twins with 45,X/46,XY mosaicism, discordant for phenotypic sex, are extremely rare. METHODS: This report describes the clinical findings of a rare case of 45,X/46,XY mosaicism in monozygotic twins with different external genitalia. Single nucleotide polymorphism (SNP) array analysis, performed by collecting DNA from each umbilical cord, showed identical SNPs in the autosomal chromosomes of both fetuses. RESULTS: Chorionic villus sampling of a 37-year-old primigravida carrying monozygotic twins revealed a 45,X/46,XY karyotype. Autopsy of the aborted fetuses revealed a penis and testes on one fetus and a vagina, uterus, and ovaries in the other fetus--which also had severe cystic hygroma. Cell counting using fluorescence in situ hybridization with XY probes (XY-FISH) showed 20% and 80% abundance of 45,X cells in the internal genitalia, liver, heart, lung, adrenal gland, bone marrow, and spine of the male and female fetuses, respectively. CONCLUSION: These results indicated that the fetuses were genetically monozygotic twins and their different degrees of mosaicism may have resulted in different genital phenotypes.

Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism.

OBJECTIVE: To describe the gonadal features of patients with 45,X/46,XY mosaicism, and to evaluate the prevalence of gonadal tumor in different phenotypes. MATERIALS AND METHODS: The medical records of consecutive patients with 45,X/46,XY karyotype or its variants who had undergone gonadal biopsy or gonadectomy at a single institute between 1996 and 2017 were retrospectively reviewed. RESULTS: Of 34 patients with 45,X/46,XY mosaicism, a unilateral dysgenetic testis and a contralateral streak gonad was detected in 20 patients (59%), bilateral streak gonads in 9 (26%), and bilateral dysgenetic testes in 5 (15%). A gonad composed of both streak and dysgenetic testicular portions was observed in 7 gonads of 6 patients. All streak gonads were removed, and bilateral gonadectomy was performed in 15 patients raised as girls. Pathologic examination revealed gonadal tumors in 6 of the 34 (18%) patients, including a gonadoblastoma in 7 gonads among 5 patients and an association of dysgerminoma with gonadoblastoma in 1 gonad. All 6 patients who developed gonadal tumor had female genitalia. Postoperative course was uneventful except 1 boy. A seminoma was developed in his soritaly scrotal testis at the age of 16 years. CONCLUSION: The prevalence of gonadal tumor in patients with 45,X/46,XY mosaicism may vary according to the phenotype, and high in patients with female phenotype. Considering the increased risk of gonadal tumors in such patients, early investigation and individual management, including prophylactic gonadectomy, are recommended. In male patients, a close follow-up of the preserved testes is mandatory until adulthood.

Atypical Presentation of Swyer Syndrome.

BACKGROUND: Swyer syndrome is a rare type of disorder of sex development and typically presents with delayed puberty and primary amenorrhea. We describe an unusual presentation of this condition. CASE: A 17-year-old female patient with typical thelarche and adrenarche presented with primary amenorrhea. Pelvic ultrasound showed normally developed uterus and bilateral ovoid hypoechoic structures suggestive of gonads. Laboratory investigations revealed highly elevated gonadotrophins with estradiol level within a range typical for a female of reproductive age and chromosome analysis showed a 46,XY karyotype. Histopathological examination of the gonadectomy specimens revealed gonadoblastoma and dysgerminoma with no functional ovarian or testicular tissue. SUMMARY AND CONCLUSION: This report reminds us the possibility of diagnosis of Swyer syndrome in the presence of normal pubertal development and normal sex steroid levels considered to be produced by gonadoblastoma.

'Size does matter': Prophylactic gonadectomy in a case of Swyer syndrome.

Swyer syndrome also known as pure or complete gonadal dysgenesis is a very rare disorder of sex development wherein the individuals are phenotypically females with 46, XY genotype and preserved mullerian structures. These individuals characteristically have dysgenetic streak gonads which carry an increased risk of malignant transformation. Prophylactic gonadectomy is highly recommended as soon as a clinical diagnosis is established to diminish the chances of tumor development. We present a case of complete gonadal dysgenesis with bilateral small gonads with a dysgerminoma arising in a background of gonadoblastoma in one gonad and immature teratoma in the other. The present case, besides adding a rare case to the literature, highlights the importance of detailed pre-operative assessment of gonadal size and prompt prophylactic gonadectomy in cases with gonadal dysgenesis.

Mutations in MAP3K1 that cause 46,XY disorders of sex development disrupt distinct structural domains in the protein.

Missense mutations in the gene, MAP3K1, are a common cause of 46,XY gonadal dysgenesis, accounting for 15-20% of cases [Ostrer, 2014, Disorders of sex development (DSDs): an update. J. Clin. Endocrinol. Metab., 99, 1503-1509]. Functional studies demonstrated that all of these mutations cause a protein gain-of-function that alters co-factor binding and increases phosphorylation of the downstream MAP kinase pathway targets, MAPK11, MAP3K and MAPK1. This dysregulation of the MAP kinase pathway results in increased CTNNB1, increased expression of WNT4 and FOXL2 and decreased expression of SRY and SOX9. Unique and recurrent pathogenic mutations cluster in three semi-contiguous domains outside the kinase region of the protein, a newly identified N-terminal domain that shares homology with the Guanine Exchange Factor (residues Met164 to Glu231), a Plant HomeoDomain (residues Met442 to Trp495) and an ARMadillo repeat domain (residues Met566 to Glu862). Despite the presence of the mutation clusters and clinical data, there exists a dearth of mechanistic insights behind the development imbalance. In this paper, we use structural modeling and functional data of these mutations to understand alterations of the MAP3K1 protein and the effects on protein folding, binding and downstream target phosphorylation. We show that these mutations have differential effects on protein binding depending on the domains in which they occur. These mutations increase the binding of the RHOA, MAP3K4 and FRAT1 proteins and generally decrease the binding of RAC1. Thus, pathologies in MAP3K1 disrupt the balance between the pro-kinase activities of the RHOA and MAP3K4 binding partners and the inhibitory activity of RAC1.

45,X/46,XY Mosaicism Presenting With Isolated Unilateral Cryptorchidism and a Normal Blood Karyotype.

Context: 45,X/46,XY mosaicism is a disorder of sex development leading to abnormal gonadal development and to unpredictable genital phenotype, growth, and pubertal development. Case Description: A 2-year-old male presented with a right impalpable testis. Blood karyotype was 46,XY. A laparoscopy performed for right orchidopexy revealed a right streak gonad with Mullerian structures, whereas on the left side, a normal descended testis was present. The karyotype of the removed gonad was 45,X/46,XY. The child grew along the second centile, within the midparental height (MPH) range, until the time of puberty, when linear growth worsened due to a lack of a pubertal growth spurt, and growth hormone (GH) therapy was initiated. He developed spontaneous puberty (13 years of age) and showed normal pubertal progression. However, from the age of 15 years, he had low normal testosterone, raised follicle-stimulating hormone, and reduction of inhibin B, possibly suggestive of declining testicular function. His final height was -2.24 standard deviation score (SDS) (-2.4 SDS at GH start; MPH -1.6 SDS). Conclusions: Our case describes a mild male phenotype associated with 45,X/46,XY mosaicism characterized by unilateral cryptorchidism, spontaneous onset of puberty, and normal blood karyotype. The case illustrates the difficulties inherent in making a diagnosis of 45,X/46,XY mosaicism when there is no genital ambiguity and makes the point that growth and testicular impairment may occur, mostly manifesting during adolescence. An early diagnosis is crucial to initiate careful monitoring for growth and pubertal disorders, increased tumor risk, and fertility issues commonly seen in these children.

Presence of viable germ cells in testicular regression syndrome remnants: Is routine excision indicated? A systematic review.

There is no consensus in the literature about the necessity for excision of testicular remnants in the context of surgery for an impalpable testis and testicular regression syndrome (TRS). The incidence of germ cells (GCs) within these nubbins varies between 0 and 16% in previously published series. There is a hypothetical potential future malignancy risk, although there has been only one previously described isolated report of intratubular germ-cell neoplasia. Our aim was to ascertain an accurate incidence of GCs and seminiferous tubules (SNTs) within excised nubbins and hence guide evidence-based practice. The systematic review protocol was designed according to the PRISMA guidelines, and subsequently published by the PROSPERO database after review (CRD42013006034). The primary outcome measure was the incidence of GCs and the secondary outcome was the incidence of SNTs. The comprehensive systematic review included articles published between 1980 and 2016 in all the relevant databases using specific search parameters and terms. Strict inclusion and exclusion criteria were ultilised to identify articles relevant to the review questions. Twenty-nine paediatric studies with a total of 1455 specimens were included in the systematic review. The mean age of the patients undergoing nubbin resection was 33 months and the TRS specimen was more commonly excised from the left (68%). The incidence of SNTs was 10.7% (156/1455) and the incidence of GCs, 5.3% (77/1455). Histological analysis excluding the presence of either SNTs or GCs was consistent with TRS, fibrosis, calcification or haemosiderin deposits. There is limited evidence on subset analysis that GCs and SNTs may persist with increasing patient age. This systematic review has identified that 1 in 20 of resected testicular remnants has viable GCs and 1 in 10 has SNTs present. There is insufficiently strong evidence for the persistence of GCs and SNTs with time or future malignant potential. Intra-abdominal TRS specimens may contain more elements and, therefore, require excision, although this is based on limited evidence. However, there is no available strong evidence to determine that a TRS specimen requires routine excision in an inguinal or scrotal position.

17α-HYDROXYLASE/17, 20-LYASE DEFICIENCY: CLINICAL AND MOLECULAR CHARACTERIZATION OF EIGHT CHINESE PATIENTS.

OBJECTIVE: 17α-hydroxylase/17, 20-lyase deficiency (17OHD) is caused by mutations in the cytochrome P450 17A1 (CYP17A1) gene. To better understand 17OHD, a rare disease, we described the clinical features and performed CYP17A1 gene analysis in 8 affected Chinese patients. METHODS: Patients with complete (7/8) or partial (1/8) 17OHD were derived from 6 families. The diagnosis was established according to their clinical, biochemical, hormonal, and radiological characteristics. Long-term follow-up of some patients was also designed. RESULTS: Patients with 17OHD suffered from varying degrees of hypokalemia and hypertension. Symptoms in female patients with partial 17OHD manifested as secondary amenorrhea, recurrent ovarian cysts, elevated estradiol level, and lower follicle-stimulating hormone and luteinizing hormone levels; primary amenorrhea was typical in patients with complete 17OHD. Adrenal masses and decreased bone mineral density (BMD) were discovered in 2 patients, respectively. During long-term follow-up, 4 patients developed low BMD, while 3 individuals underwent respiratory infections and recurrent urinary tract infections. CYP17A1 gene analysis revealed 7 different kinds of mutation, including 1 novel mutation, L266V. CONCLUSION: The clinical characteristics of partial 17OHD were different from those of complete 17OHD. Low BMD and infections were common in patients with 17OHD on long-term steroid treatment. Seven mutations were identified in the CYP17A1 gene, and 1 was novel. ABBREVIATIONS: ACTH = adrenocorticotropic hormone BMD = bone mineral density CAH = congenital adrenal hyperplasia CT = computed tomography DEXA = dual-energy X-ray absorptiometry DEX = dexamethasone 17OHD = 17α-hydroxylase/17, 20-lyase deficiency.

A Novel Missense Mutation 224G>T (R75M) in SRY Coding Region Interferes with Nuclear Import and Results in 46, XY Complete Gonadal Dysgenesis.

SRY-mutation-caused sex reversal is a rare disease and mostly associated with a de novo mutation since the patients with defective SRY is infertile. There are many reports about SRY-mutation associated 46, XY ovarian disorder of sex development (DSD), but few described their molecular mechanism. Here we report a de novo mutation 224G>T (R75M) in SRY associated with a phenotypic female, 46, XY karyotype and dysgerminoma. The wild and mutated SRY were cloned into recombinant plasmid and expressed in cells in vitro, the result showed the mutated SRY is greatly accumulated in cytoplasm while the wild type SRY is mostly localized in nucleus. To make sure no other genes were involved, we performed the trio-based whole exome sequencing using the DNA samples from the proband and the parents, and no mutations were identified especially in DHH, NR0B1, NR5A1, SOX9 and MAP3K1, indicating the de novo mutation in SRY is the single defect responsible for the female sex reversal. We also used bioinformatics simulation analysis to predict impact of the mutation on SRY function, and find the R75 in wild type SRY can form a hydrogen bond with serine at 91 (S91) that make the SRY protein well fit into the minor groove of target DNA, while the M75 in the mutated SRY can't. Finally, we reviewed SRY mutations based on the available references and analyzed the mutation distribution patterns according to density and continuity, which may be useful for further study of the SRY structure, function, and its relatedness with DSD.

An Unusual Presentation of 46,XY Pure Gonadal Dysgenesis: Spontaneous Breast Development and Menstruation.

46,XY pure gonadal dysgenesis (Swyer syndrome) is characterized by normal female genitalia at birth. It usually first becomes apparent in adolescence with delayed puberty and amenorrhea. Rarely, patients can present with spontaneous breast development and/or menstruation. A fifteen-year-old girl presented to our clinic with the complaint of primary amenorrhea. On physical examination, her external genitals were completely female. Breast development and pubic hair were compatible with Tanner stage V. Hormonal evaluation revealed a hypergonadotropic state despite a normal estrogen level. Chromosome analysis revealed a 46,XY karyotype. Pelvic ultrasonography showed small gonads and a normal sized uterus for age. SRY gene expression was confirmed by multiplex polymerase chain reaction. Direct sequencing on genomic DNA did not reveal a mutation in the SRY, SF1 and WT1 genes. After the diagnosis of Swyer syndrome was made, the patient started to have spontaneous menstrual cycles and therefore failed to attend her follow-up visits. After nine months, the patient underwent diagnostic laparoscopy. Frozen examination of multiple biopsies from gonad tissues revealed gonadoblastoma. With this report, we emphasize the importance of performing karyotype analysis, which is diagnostic for Swyer syndrome, in all cases with primary or secondary amenorrhea even in the presence of normal breast development. We also suggest that normal pubertal development in patients with Swyer syndrome may be associated with the presence of a hormonally active tumor.

46,XY Gonadal Dysgenesis due to a Homozygous Mutation in Desert Hedgehog (DHH) Identified by Exome Sequencing.

BACKGROUND: 46,XY disorders of sex development (DSD) comprise a heterogeneous group of congenital conditions. Mutations in a variety of genes can affect gonadal development or androgen biosynthesis/action and thereby influence the development of the internal and external genital organs. OBJECTIVE: The objective of the study was to identify the genetic cause in two 46,XY sisters of a consanguineous family with DSD and gonadal tumor formation. METHODS: We used a next-generation sequencing approach by exome sequencing. Electrophysiological and high-resolution ultrasound examination of peripheral nerves as well as histopathological examination of the gonads were performed. RESULTS: We identified a novel homozygous R124Q mutation in the desert hedgehog gene (DHH), which alters a conserved residue among the three mammalian Hedgehog ligands sonic hedgehog, Indian hedgehog, and desert hedgehog. No other relevant mutations in DSD-related genes were encountered. The gonads of one patient showed partial gonadal dysgenesis with loss of Leydig cells in tubular areas with seminoma in situ and a hyperplasia of Leydig cell-like cells expressing CYP17A1 in more dysgenetic parts of the gonad. In addition, both patients suffer from a polyneuropathy. High-resolution ultrasound revealed a structural change of peripheral nerve structure that fits well to a minifascicle formation of peripheral nerves. CONCLUSION: Mutations in DHH play a role in 46,XY gonadal dysgenesis and are associated with seminoma formation and a neuropathy with minifascicle formation. Gonadal dysgenesis in these cases may be due to impairment of Sertoli cell-Leydig cell interaction during gonadal development.

Is routine excision of testicular remnants in testicular regression syndrome indicated?

BACKGROUND: Undescended testicles are a common finding in full-term male infants. In the majority of these infants, the testicle spontaneously descends in the first year of life. However, in others, it remains impalpable in an abnormal position or there may only be a small abnormal testicular remnant present. For these infants there is still controversy surrounding inguinal exploration and/or excision of these testicular remnants at the time of operative intervention. The controversy centres on their potential future malignant potential. AIM: The aim of the study was to ascertain the incidence of the presence of either germ cells (GCs) or seminiferous tubules (SNTS) in the excised testicular remnants. This was performed at a paediatric surgical tertiary centre and contributes to the evidence base for this condition. METHOD: A retrospective data analysis occurring over a 15-year period of all excised testicular remnants. The testicular remnants were analysed for age, laterality, histological analysis and clinical diagnosis. Subset analysis included subdivision into both intra-abdominal or inguinal positions, and age ranges. Statistical analysis was using Fisher's exact test and a P-value of <0.05 was considered to be significant. RESULTS: A total of 140 paediatric male patients were identified as having had a testicular remnant excised during the study period. Their demographics and also the main results are summarised in the overall summary Table. The mean age at intervention was 3.5 years (range: 3 months to 17 years). A total of 132/140 of the boys underwent excision of an inguinal testicular regression syndrome (TRS) remnant and 8/140 an intra-abdominal remnant. Comparison of these two groups revealed no significant difference for the presence of GCs (12 (9%) vs 2 (25%), P = 0.18). However, intra-abdominal TRS remnants were much more likely to contain SNTs (27 (21%) vs 7 (88%), P = 0.0002). There was no decreased incidence of either GCs or SNTs with increased patient age. DISCUSSION: The main reason for the debate over the management of boys with TRS is the variable incidence of viable germ cells reported in different studies: it has been reported between 0 and 16%. The incidence of GCs (10%) and also SNT (24%) in the present series therefore contributes to this evidence base and is in the middle of this range. It is still unclear as to whether these remnants have a future malignancy risk, as there is only one case of intratubular germ cell neoplasia (ITGCN) in a testicular remnant reported in the literature and this was not immunohistochemically supported. The presence of ITGCN, although considered as a precursor to the development of a testicular germ cell tumour in adult patients, has also not been established in paediatric patients. The natural history of the GCs in TRS specimens is also unknown. In the present series, however, there was no decreased incidence demonstrated with increased patient age, although older patient numbers limited this subset analysis. Despite this controversy, as these patients were already under general anaesthetic, an inguinal exploration and excision of any TRS remnant that was present did not significantly increase the operative procedure or time, and removed any potential malignancy risk. CONCLUSION: This evidence supports the exploration and excision of inguinal testicular remnants, as one in ten boys have GCs present and one in four have SNTs, which may have a potential future malignant transformation risk.

A Novel SRY Gene Mutation p.F109L in a 46,XY Female with Complete Gonadal Dysgenesis.

46,XY complete gonadal dysgenesis (CGD) is a disorder of sexual development that can result from different mutations in genes associated with sex determination. Patients are phenotypically females, and the disease is often diagnosed in late adolescence because of delayed puberty. Here, we present the clinical and molecular data of a 46,XY female CGD patient with gonadoblastoma with dysgerminoma and incidentally found inherited thrombophilia. The clinical significance of the described de novo SRY gene mutation c.325T>C (p.F109L) is discussed. This case report supports the critical role of the HGM domain in the SRY gene and the need of a multidisciplinary approach for CGD patients.

Swyer syndrome.

PURPOSE OF REVIEW: This review focuses on the pathogenesis, diagnosis, management and long-term outcomes of disorders of sex development, specifically women with Swyer syndrome (46,XY complete gonadal dysgenesis). RECENT FINDINGS: Recent discoveries have broadened our understanding of the complex pathways involved in normal and abnormal sex development. In 46,XY gonadal dysgenesis, lack of testis development may be triggered by sex determining region Y, NR5A1, DHH or testis-determining gene loss-of-function mutations, DAX1 or WNT4 duplication or MAP3K1 gain-of-function mutations. The diagnosis and management of patients with Swyer syndrome is complex, and optimal care requires an experienced multidisciplinary team. Early diagnosis is vital because of the significant risk of germ cell tumour, and bilateral gonadectomy should be performed. Furthermore, early sex hormone treatment is necessary to induce and maintain typical pubertal development and to achieve optimal bone mineral accumulation. Pregnancy is possible via ova donation, and outcomes are similar to women with 46,XX ovarian failure. SUMMARY: Further pathogenic gene mutations are likely to be identified, and the function, interaction and phenotypic effects of new and existing mutations will be further defined. Patients require long-term follow-up in specialist centres.