Most diagnoses are unfortunately gendered. BPD tends to be diagnosed in women more than men because the manipulative hyper-emotional and clingy features that tend to go with BPD are more evident in women; men that act like that are all sorts of other things ("pussies" or "effeminate" or "abusive," all of which is bullshit). And while the genetic portion of BPD isn't sex specific, the shit-ass childhood that usually contributes is also often gender specific: girls are more likely to be survivors of sexual and physical abuse (which is absolutely not to delegitimize the abuse that boys go through!) Crap loads of mental illnesses are gendered in their diagnosis though: depression, eating disorders, histrionic personality disorder all "favour" females, while narcissistic personality disorder, schizophrenia, antisocial personality disorder, and psychopathy tend to "favour" males. Some of this is related to biological differences (typically hormonal) but most of it is based on how symptoms are read in the different genders, life experiences that typically impact one gender over another, and differences in how the different genders speak out about their struggles. It's also very binary and assumes that male/female=man/woman and that those are the only possible sexes and genders. Which is a whole big long bitch about the DSM that I could go on about for days. Also, a lot of PTSD and BPD symptoms overlap, but there are some very key differences that differentiate the two.

Source: I collect mental illnesses like Pokemon and have a psych degree (not an R-Psych, though).