Complete androgen insensitivity syndrome
| Complete androgen insensitivity syndrome | |
|---|---|
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| AIS results when the function of the androgen receptor (AR) is impaired. The AR protein (pictured) mediates the effects of androgens in the human body. | |
| Classification and external resources | |
| Specialty | endocrinology |
| ICD-10 | E34.51 |
| ICD-9-CM | 259.51 |
| OMIM | 312300 300068 |
| DiseasesDB | 29662 12975 |
| eMedicine | ped/2222 |
| MeSH | D013734 |
| GeneReviews | |
Complete androgen insensitivity syndrome (CAIS) is a condition that results in the complete inability of the cell to respond to androgens. The unresponsiveness of the cell to the presence of androgenic hormones prevents the masculinization of male genitalia in the developing fetus, as well as the development of male secondary sexual characteristics at puberty, but does not significantly impair female genital or sexual development. As such, the insensitivity to androgens is only clinically significant when it occurs in genetic males (i.e. individuals with a Y chromosome, or more specifically, an SRY gene). All affected individuals are phenotypically female; they develop a normal female habitus, despite the presence of a Y chromosome.
CAIS is one of the three categories of androgen insensitivity syndrome (AIS) since AIS is differentiated according to the degree of genital masculinization: complete androgen insensitivity syndrome (CAIS) when the external genitalia is that of a normal female, mild androgen insensitivity syndrome (MAIS) when the external genitalia is that of a normal male, and partial androgen insensitivity syndrome (PAIS) when the external genitalia is partially, but not fully masculinized.
Androgen insensitivity syndrome is the largest single entity that leads to 46,XY undermasculinization.
Individuals with complete androgen insensitivity syndrome (grades 6 and 7 on the Quigley scale) are born phenotypically female, without any signs of genital masculinization, despite having a 46,XY karyotype. Symptoms of CAIS do not appear until puberty, which may be slightly delayed, but is otherwise normal except for absent menses and diminished or absent secondary terminal hair.Axillary hair (i.e. armpit hair) fails to develop in one third of all cases. External genitalia is normal, although the labia and clitoris are sometimes underdeveloped. The vaginal depth varies widely, but is typically shorter than unaffected women; one study of eight women with CAIS measured the average vaginal depth to be 5.9 cm (vs. 11.1 ± 1.0 cm for unaffected women ). In some extreme cases, the vagina has been reported to be aplastic (resembling a "dimple"), though the exact incidence of this is unknown.
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