An inherited condition also known as congenital adrenal hyperplasia, which affects about 1 baby in 7,500. It causes various ENZYME defects as well as blocking the production of HYDROCORTISONE and ALDOSTERONE by the ADRENAL GLANDS. In girls the syndrome produces VIRILISATION of the genital tract, often with gross enlargement of the clitoris and fusion of the labia so that the genitalia may be mistaken for a malformed penis. The metabolism of salt and water may be disturbed, causing dehydration, low blood pressure and weight loss; this can produce collapse at a few days or weeks of age. Enlargement of the adrenal glands occurs and the affected individual may also develop excessive pigmentation in the skin.

When virilisation is noted at birth, great care must be taken to determine genetic sex by blood testing. Blood levels of adrenal hormones are measured to refine the diagnosis. Traditionally doctors had advised parents to ‘choose’ their child's gender on the basis of discussing the likely condition of the genitalia after puberty. Thus, where the phallus was thought likely to be inadequate as a male organ, advice might be to rear the child as female. Controversy remains and it is essential that an experienced paediatric endocrinologist discusses all options with the family. Surgery is often recommended in the first two years to deal with clitoromegaly but parent/patient pressure groups have pointed out the ethical dilemma of operating on children too young to consent. Other treatment requires replacement of the missing hormones which, if started early, may lead to normal sexual development. There is still controversy surrounding the ethics of gender reassignment because of the problems some patients develop in adolescence and adult life in adjusting to their sexuality.