What Causes White Patches On Upper Thighs?

I have these white patches on both sides of my upper thighs, sometimes they look red and sometimes i can barely see them..sometimes they look scaley but not always, i went to a derm. last year and he said it was pittyrias rosecea but that was before it spread to my other thigh, I have psoriasis on my finger nalis so maybe its early psoriasis?