This is years later and I'm sorry I couldn't have helped sooner. I have the same type of spot in the same location you specified as well as another on the top of my opposite foot. It's been diagnosed as Granuloma Annulare. Unfortunately Ive had it for about a year now. I started seeking answers to what it was 6 months after it apeared. Now another 6 has gone by and it hasn't gotten better. The Dermatologist started with a steroid cream and that hasn't helped. I'm waiting to hear the next course of action.
I have started walking and when I would come home found that my legs itched insatiably and would swell up like hives. Eventually they became blotches on my calves. Then I noticed a quarter size purple red spot on the top of my foot. Then 2 dime sized circles on my hand. The foot purple mark enlarged three times the orig. size. The ones on my hand I had a dermatologist inject with cortizone, which sorta killed the disease and stopped the ich. My legs now after about 2 years are a purple blotchy mess different than the circles on my hand. Under my arms there is a double ring like 50 cent pieces.
I have them on my outer thighes and inside of them. I asked the doctor if this all is the same thing and she said yes but they look different. I was also told that they connect this with a possible thyroid problem or diabetes. I am terrified that it will come on my face since it seems to have no boundaries. I am 62 years old....why now?