Disorders/differences of sex development (DSD) are conditions where the development of chromosomal, anatomical or gonadal sex is atypical. DSD covers a wide spectrum of disorders such as hypospadias (misplacement of the urethral opening on the penis), premature ovarian insufficiency and complete sex reversal (where the physical sex does not match the genetic sex of an individual).
DSD cases are surprisingly common, with a frequency of 1 in 4,500 births. The underlying cause of many DSD cases is the failure of genes responsible for the proper development of the reproductive organs during fetal development. Unfortunately, the underlying genetic cause of around 70% of DSD cases is unknown.