Undervirilized fertile male syndrome (Mild Androgen Insensitivity Syndrome)

Some AR mutations with mildly reduced sensitivity cause mild undervirilization. These men have normally formed internal and external genitalia but often a small penis. Androgenic body hair may be sparser than unaffected relatives. Ejaculate volume may be reduced, though sperm density is normal. Few examples of this variant of AIS have been reported, but unlike the previously listed phenotypes, many of these men are fertile. Also, individuals with this condition may experience gynecomastia during puberty.