What condition is indicated by a 3-month-old girl presenting with bilateral inguinal hernias, shallow vagina, and a karyotype of 46,XY?

The scenario describes a case of a 3-month-old girl with features suggestive of androgen insensitivity syndrome, which is linked to a defective androgen receptor. This condition occurs due to an XY karyotype (male chromosomes) combined with the presence of characteristics typical for females, such as the shallow vagina and bilateral inguinal hernias.

In this condition, the presence of the Y chromosome normally leads to the development of testes; however, if the androgen receptors are defective, the body cannot respond to male hormones (androgens) like testosterone. Although the testes are present and may produce testosterone, the lack of response due to the faulty receptors results in the development of female external genitalia. The shallow vagina can also indicate a lack of other anatomical features associated with male development due to ineffective androgen signaling.

The inguinal hernias result from the failed closure of the processus vaginalis, which can occur since there is improper development of the male structures. Despite the XY chromosomal makeup, the phenotype reflects a more female presentation due to the absence of effective testosterone action.

This all points toward a diagnosis of androgen insensitivity syndrome, confirming that the correct answer is related to defective androgen receptors.