""Gender dysphoria" is a type of body dysmorphia/body integrity identity disorder, a subtype of OCD. As with BD/BIID, the person's OCD forces them to focus on their body and how "wrong" it is, in this case "wrong" in terms of sexual characteristics. This leads to intense distress and attempts to "correct" what's "wrong" with self mutilation or extensive surgery. The development of GD/BD/BIID can get kickstarted by any number of factors. A few might include childhood sexual abuse, autism leading to social incompatibility, external social pressures, or abysmally low self esteem with escapism.
This issue may affect anyone but most often introverted/passive/anxious people who are vulnerable to any type of OCD anyway.
It's worsened by encouragement and body modification, the distress does not go away, the thoughts merely latch onto any new percieved "flaw" and this can cause depression/suicide."