How geneticists think about Differences/Disorders of Sexual Development (DSD): A conversation

Precision medicine and rare diseases in pediatric urology

Precision Medicine holds promise for helping us manage specific phenotypes of common diseases. For rare diseases such as hypospadias, DSD, and pediatric solid tumors, it can also reveal underlying risk factors and pathogenesis. Professors Ann Nordgren and Anna Lindstrand share their experiences in the development and ongoing initiatives of the Swedish national project on Precision Medicine and how it could change the care of pediatric urology patients.

Congenital Micropenis: Etiology And Management

In the newborn, penile length is determined by a number of androgen dependent and independent factors. The current literature suggests that there are interracial differences in stretched penile length in the newborn and although congenital micropenis should be defined as a stretched penile length of less than 2.5 SDS of the mean for the corresponding population and gestation, a pragmatic approach would be to evaluate all boys with a stretched penile length below 2 cm, as congenital micropenis can be a marker for a wide range of endocrine conditions. However, it remains unclear as to whether the state of micropenis, itself, is associated with any long-term consequences. There is a lack of systematic studies comparing the impact of different therapeutic options on long-term outcomes, in terms of genital appearance, quality of life, and sexual satisfaction. To date, research has been hampered by a small sample size and inclusion of a wide range of heterogeneous diagnoses; for these reasons, condition-specific outcomes have been difficult to compare between studies. Lastly, there is a need for a greater collaborative effort in collecting standardized data so that all real-world or experimental interventions performed at an early age can be studied systematically into adulthood.

Establishing a molecular genetic diagnosis in children with Differences of Sex Development - a clinical approach

Background Despite distinct underlying aetiologies, the clinical phenotypes and hormonal profiles of children with various differences of sex development (DSD) are often similar, which presents challenges to ascertaining an accurate diagnosis on clinical grounds alone. Associated features and important clinical outcomes can, however, vary significantly in different DSD, thus establishing an accurate molecular diagnosis may have important implications for decision-making and management planning in a given individual. Summary The wider availability of next generation sequencing techniques in recent years has led to recommendations for earlier integration of genetic testing in the diagnostic pathway of children with DSD. This review provides a practical overview of the clinical applications, advantages and limitations of the more commonly available diagnostic genetic tests and outlines a suggested approach to testing. The potential clinical implications of a confirmed genetic diagnosis on subsequent management pathways for individuals with DSD, as well as challenges that remain to be addressed are also outlined. Key messages Despite significant improvements in our understanding of the complex genetic pathways that underlie DSD, an accurate diagnosis still eludes many affected individuals. Establishing a molecular diagnosis provides aetiological certainty, enabling improved information for families and individualised clinical management, including monitoring or prophylactic intervention where higher longer-term health risks exist. A stepwise approach to genomic testing is recommended to afford highest diagnostic yield from available resources. Looking forward, collaborative multicentre prospective studies will be required to assess the true impact of a genetic diagnosis on improving clinical care pathways and health, wellbeing and patient-reported outcomes for individuals with DSD.

Differences of sex development in the newborn: from clinical scenario to molecular diagnosis

Differences/disorders of sex development (DSD) are defined as a group of congenital conditions in which the development of chromosomal, gonadal or anatomical sex is atypical. The incidence of DSD is 1:4500 births. The current classification divides DSDs into 3 categories according to chromosomal sex: 46,XX DSD, 46,XY DSD and sex chromosome DSD. DSD phenotypes can be concordant with the genotype (apparently normal external genitalia associated with gonadal dysgenesis), or can range from simply hypospadias to completely masculinised or feminised genitalia with a discordant karyotype. Numerous genes implicated in genital development have been reported. The search of genetic variants represents a central element of the extended investigation, as an improved knowledge of the genetic aetiology helps the immediate and long-term management of children with DSDs, in term of sex of rearing, hormone therapy, surgery, fertility and cancer risk. This review aims to assess the current role of molecular diagnosis in DSD management.

How Far Should We Explore Hypospadias? Next-generation Sequencing Applied to a Large Cohort of Hypospadiac Patients

BACKGROUND

Next-generation sequencing (NGS) is generally used for patients with severe disorders of sex development (DSD). However, NGS has not been applied extensively for patients with hypospadias only, and most affected children do not benefit from an etiological diagnosis.

OBJECTIVE

To evaluate the clinical usefulness of NGS for patients with hypospadias, regardless of severity.

DESIGN, SETTING, AND PARTICIPANTS

Prospective multicenter research included 293 children with glandular to penoscrotal hypospadias (no undescended testis and no micropenis). After excluding likely pathogenic androgen receptor (AR) variants by Sanger sequencing, an NGS panel tested 336 genes including unexplored candidates in 284 patients.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The rate of pathogenic and likely pathogenic variants was assessed using REVEL, ClinVar, and in-house tools (Captain-ACHAB, MobiCNV, and MobiDetails).

RESULTS AND LIMITATIONS

Likely pathogenic variants were identified in 16 (5.5%) patients with both Sanger sequencing and NGS taken into account. Some genes were related to DSD (AR, NR5A1, HSD17B3, and MAMLD1), but reverse phenotyping revealed two syndromic disorders with midline defects (MID1) and alteration in the retinoic acid signaling pathway (RARA). Coverage analysis revealed an 18q deletion. Identification of likely pathogenic variants increased with hypospadias severity. Other variants of unknown significance (VUSs) in genes implicated in hypogonadotropic hypogonadism, Noonan syndrome, and genital tubercle development were also identified. Genetic study mainly focused on exonic variants, and most cases remain unexplained.

CONCLUSIONS

NGS reveals minor forms of DSD, undiagnosed syndromes, or candidate rare variants in new genes, indicating that even patients with mild hypospadias benefit from advanced sequencing techniques. Early molecular diagnosis would help improve follow-up at puberty and medical counseling for initially undiagnosed syndromes. Future studies will improve the diagnosis by investigating the contribution of VUSs.

PATIENT SUMMARY

Next-generation sequencing enables simultaneous testing of numerous genes and should not be limited to disorders of sex development cases. Even patients with mild hypospadias would benefit from early diagnosis of a genetic defect implicated in sex development or other syndromes.