It's a disorder which prevents masculinization of the body, even if the person in question has a Y chromosome. For genotypic females (XX chromosomes), it hardly does anything, as it doesn't impair female sexual organ growth (we all start out as females at the fetal status anyway) but for genotypic males (XY chromosomes) it can result in either:
- Complete AIS: A person who is essentially a woman, having all the external female genitalia. She/he has underdeveloped testicles which are hidden, lacks ovaries and a uterus, thus being infertile. Often it presents with (ironically enough) increased female traits; round hips, clear skin and larger breasts. Secondary male sexual characteristics do not present either, most often lack pubic hair, and naturally there's no menses.
- Partial AIS: A person who has partially developed external male genitalia. It could range from close to CAIS, to close to MAIS (below) in both that and the traits mentioned above.
- Mild AIS: A person who has normal male external genitalia. This usually only presents with infertility, and is much rarer.
The interesting thing is, a person with CAIS can effectively live an entire life without knowing they are genotypically a male, since external female development happens normally (or better than normal), that fact is what got me interested in it. Though I reckon most would check for what's causing missing menses, or in some cases a minuscule vaginal depth - or cancer in the undeveloped and undiscovered testes (which is quite common).