I am going through the same thing, i am african american so my spots are dark in color. i look like a lepord, my lesg and arms. i went to the derm. and i found that i may have : Bullous pemphigoid. its a rare skin disease that 1 and evrey 2,000 people this happens to. it is a rare dises, many doctors have never seen this. check this site out.
http://www.mayoclinic.com/health/bullous-pemphigoid/DS00722
I hope it helps, i know i do not know you but i feel you pain!
p.s sorry not the best speller!
I thought was jock itch. I used some o.t.c. stuff as prescribed. it didn't help. After a month I went to my Derm. He prescribed cortisone & almost immediately it got better. then, after another few weeks I started noticing the skin getting lighter where it was. and then all pigment was gone. I had 2 large (like a pencil erasure spots size) 2 smaller and one very small white spots. He said some times peoples immune systems go into over-drive (like mine. many many years ago I had a mild case of coup de sabre or morphea.) sometimes when the immune system attacks it doesn't stop at the pathogen. It can continue devouring our cells: fat, hair and pigment cells ( vitiligo (leucoderma. think Michael Jackson)
Derm Rx'd Protopic and after 4-6 weeks the color is returning.
Michael*