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.