White Spots On Skin Photo Bizarre Skin Discoloration?

Bizarre skin discoloration? - white spots on skin photo

He is a palomino gelding and for some reason, the skin under the hind legs and tail / Around the vagina is discolored. How gray instead of the normal, has white spots. It seems that the color of an Appaloosa with a diploma. It causes no discomfort or itching. The number of points seem to multiply. He is a purebred, registered, DNA testing, Morgan and ten years. Is this something to worry about? What is the cause?

Sorry, no photos.