Partial androgen insensitivity syndrome
Partial androgen insensitivity syndrome (PAIS) is a disorder of sex development that affects the growing reproductive and genital organs of a fetus. Androgen insensitivity refers to the inability of the body of an individual with a 46, XY karyotype (usually leading to normal male development) to properly respond to male sex hormones (androgens). In PAIS, the body partially responds to these hormones.
The extent of androgen insensitivity in 46 XY individuals is quite variable, even in a single family. Partial androgen insensitivity typically results in "ambiguous genitalia." The clitoris is large or, alternatively, the penis is small and hypospadic (these are two ways of labeling the same anatomical structure). Partial androgen insensitivity may be quite common, and has been suggested as the cause of infertility in many men whose genitals are of typically male appearance.
PAIS 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.
