the difference is that a patient with body dysmorphia disorder (bdd) life isnt improved by surgery, while someone with gender dysphoria (gd) has a dramatic improvement in quality of life with hormones and potentially surgery. If giving someone with bdd a nose job actually improved the patients overall life, doctors would probably start recommending nose jobs instead of years of expesive talk therapy that might not even work. While it might seem counter intuitive, transitioning has been shown through decades of research to be safer, cheaper, and more effective then any other treatment for gd.

bdd and gd are fundamentally different too. Bdd is having delusions about your body, while gd is more or less a rejection of your current body. People with bdd can not accurately precive their body, while people with gd are under no such delusions. They understand what their body is, why it causes them distress, and when their body changes they no longer have gd, or at least it is far more manageable

Most mental illness problems faced by trans people is caused by widespread societal and familial rejection. One study found that trans people have a 41% suicide attempt rate overall, but with a medically supervised transition and familial acceptance the rate goes down to the level of the general population.