Last year, I noticed after some months that I had a dark spot on the top of each hand. I had just been diagnosed with RA (after having also had fibromyalgia for the last umpty years) and just freaked out, thinking I must be developing some awful constellation of autoimmune diseases, and was scleroderma next, and and...and I was just about to make a doctor's appointment, and then I thought, "Huh. Let's just go in the garage and look at those gloves..." Sure enough, there was a hole in between the velcro strap and the rest of the glove, and I had a little round tan mark on each hand. Sheesh.

PS The fibromyalgia has become fairly quiescent and the RA seems to be very mild indeed, mostly in the elbows.