Chromosomal Disorders of Sex Development

Abstract Chromosomal sex is, for the most part, congruently XX female and XY male. The XX and XY embryo are built on a fundamentally similar outline plan, and only as development proceeds do certain modifications evolve. If at any point in this sequential process some genetic instruction is faulty, inappropriate, or cannot be acted on, the direction of anatomical sexual development may proceed imperfectly or completely incongruently. This chapter reviews the conditions of ambiguous/incomplete/indeterminate development of the internal and external genitalia, where the basis of this is a chromosome abnormality, usually of the X or the Y chromosome. The key role of the SRY male-determining gene in a number of these conditions is noted. The de novo or familial origin of these disorders is discussed, with particular reference to possible risks of recurrence.