Can Pre Vitiligo Spreads To Scrotal Area With Pink Patches?

I was diagnosed with pre vitiligo two years go. Since then, it hasn't spread. I took some ayurvedic medicine and it worked well. What are the chances that it might spread going forward? Now, i see some kind of reddish pink patch in the skin where my scrotal sacs join the thigh. Could it be because I wear tight underwear?In addition, there is a rash and irritation at that place. In case my pre vitiligo spreads, what are the cures available for it?