At what point should we stop calling it natural and begin calling it a disorder?
Why cannot it be both?
I don't see a conflict between something being natural, yet a disorder.
To give a simple example, my hypertension is completely natural, yet I have no problem saying that it is a disorder. Nature has it's own natural way of handling hypertension, namely death. I take my prescribed medication, which is an unnatural way of handling it.
So, back to BIID. What would not seem natural for me can be quite natural for somebody with that disorder. Nature has its own way of coping. A person born blind finds his blindness quite natural, while a seeing person who lost sight later in life would find that very unnatural.
I would be inclined to say that BIID is abnormal, but not unnatural. We judge "normal" by what is common, and BIID falls outside of normal.
On the question of whether a disorder, it seems to me that the person with BIID does see it as a disorder, and the desire for amputation is an indication that the person would like to correct the disorder however he/she could.
Fundamentalism - the anti-American, anti-Christian branch of American Christianity