TIL about de la Chapelle syndrome where people with XX chromosomes are born with traditionally masculine organs & presentation. Usually those with the trait are unaware they have XX chromosomes at all
Also interesting in that regard Androgen insensitivity syndrome: Despite different root causes, it is something of the opposite of Chapelle syndrome. People who possess XY chromosomes, but possess female genitalia.
I really feel for the inevitable handful of trans men with Androgen Insensitivity syndrome. Imagine how bad it'd be if you were born with the wrong body, and couldn't change it through hormones - it'd be an actual nightmare.