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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 three types of androgen insensitivity syndrome, which is divided into three categories that are differentiated by the degree of genital masculinization: complete androgen insensitivity syndrome (CAIS) is indicated when the external genitalia is that of a normal female, mild androgen insensitivity syndrome (MAIS) is indicated when the external genitalia is that of a normal male, and partial androgen insensitivity syndrome (PAIS) is indicated when the external genitalia is partially, but not fully masculinized.〔〔〔〔〔〔〔〔〔 Androgen insensitivity syndrome is the largest single entity that leads to 46,XY undermasculinization.〔 ==Signs and symptoms== 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 is widely variable, 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.〔 The gonads in these women are not ovaries, but instead, are testes; during the embryonic stage of development, testes form in an androgen-independent process that occurs due to the influence of the SRY gene on the Y chromosome.〔〔 They may be located intra-abdominally, at the internal inguinal ring, or may herniate into the labia majora, often leading to the discovery of the condition.〔〔〔〔 Testes in affected women have been found to be atrophic upon gonadectomy.〔 Testosterone produced by the testes cannot be directly used due to the mutant androgen receptor that characterizes CAIS; instead, it is aromatized into estrogen, which effectively feminizes the body and accounts for the normal female phenotype observed in CAIS.〔 Immature sperm cells in the testes are arrested at an early stage and do not mature, since sensitivity to androgens is required in order for spermatogenesis to complete.〔〔 Germ cell malignancy risk, once thought to be relatively high, is now thought to be approximately 2%.〔 Wolffian structures (the epididymides, vasa deferentia, and seminal vesicles) are typically absent, but will develop at least partially in approximately 30% of cases, depending on which mutation is causing the CAIS.〔 The prostate, like the external male genitalia, cannot masculinize in the absence of androgen receptor function, and thus remains in the female form.〔〔〔〔 The Müllerian system (the fallopian tubes, uterus, and upper portion of the vagina) typically regresses due to the presence of anti-Müllerian hormone originating from the Sertoli cells of the testes.〔 These women are thus born without fallopian tubes, a cervix, or a uterus,〔 and the vagina ends "blindly" in a pouch.〔 Müllerian regression does not fully complete in approximately one third of all cases, resulting in Müllerian "remnants".〔 Although rare, a few cases of women with CAIS and fully developed Müllerian structures have been reported. In one exceptional case, a 22-year-old with CAIS was found to have a normal cervix, uterus, and fallopian tubes.〔 In an unrelated case, a fully developed uterus was found in a 22-year-old adult with CAIS.〔 Other subtle differences that have been reported include slightly longer limbs and larger hands and feet due to a proportionally greater stature than unaffected women,〔〔〔 larger teeth,〔〔 minimal or no acne,〔 well developed breasts,〔 and a greater incidence of meibomian gland dysfunction (i.e. dry eye syndromes and light sensitivity).〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Complete androgen insensitivity syndrome」の詳細全文を読む スポンサード リンク
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