Disorders of Sex Development (DSD)
Disorders of sex development are conditions where chromosomal, gonadal, or anatomical sex is atypical — and the newborn with ambiguous genitalia is both a diagnostic puzzle and, in one form, a life-threatening emergency.
The big picture
Disorders of sex development are conditions where chromosomal, gonadal, or anatomical sex is atypical — and the newborn with ambiguous genitalia is both a diagnostic puzzle and, in one form, a life-threatening emergency. The unifying clinical approach is to classify by karyotype and gonadal status, and the single most important reason to act fast is to catch congenital adrenal hyperplasia (CAH), where a salt-wasting crisis can kill. Building on the embryology lesson (SRY, testosterone, MIS), the logic of each condition becomes clear.
The framework: classify by karyotype (46,XX DSD / 46,XY DSD / sex-chromosome DSD), know the key conditions (CAH, androgen insensitivity, gonadal dysgenesis, Klinefelter, Turner), and recognise the CAH emergency.
Mechanism pathway
Tap any step to see why it happens.
Diagnostic algorithm
Each step answers one question. Tap to expand.
Board traps
CAH is the lifesaving diagnosis in ambiguous genitalia — 21-hydroxylase deficiency virilises 46,XX infants and causes salt-wasting crisis.
Androgen insensitivity = 46,XY + androgen-receptor defect → female phenotype despite testes (Müllerian structures still regress via MIS).
Classify DSD by karyotype + gonadal status; palpate for gonads in the newborn.
Klinefelter = 47,XXY (male, small testes, infertility); Turner = 45,X (female, gonadal dysgenesis).