The following abnormalities of sexual differentiation are important for you to recognize. The first disorder of sexual differentiation is characterized by androgen insensitivity.
Credits: Adapted with permission from Jaffe R.B. Disorders of Sexual Differentiation. In Yen S.S.C. and Jaffe R.B. eds, Reproductive Endocrinology, W.B. Saunders Co., Philadelphia, 1986, p 300.
Patients have an XY chromosomal complement, lack of mullerian structures and a blind vaginal pouch and absence of sexual hair. The syndrome is a result of an inability to respond to testosterone through a target organ androgen receptor defect (60-70%) or a post-receptor signalling defect (30-40%).
Mullerian structures are absent because the gonads secrete mullerian inhibiting substance.
The gonads may be located in the abdomen, inguinal canal, or labia. The development of gonadal neoplasia is thought to be increased to approximately 5%, however the incidence is very low before the age of 30. Routinely, orchiectomy is performed after puberty, to allow full pubertal development. Some of these patients show clitoral enlargement and labioscrotal fusion. Their condition is referred to as incomplete (partial) androgen insensitivity. These entities (complete and incomplete androgen insensitivity) are a result of mutations of genes located on the long arm of the X chromosome.