My Rheumatologist said it's part of Fibromyalgia and it just a painless rash.

Hi, I have something similar but not as dark. I have polymorphous light eruption (PLE) which causes a terrible skin rash on my arms (particularly) and legs when exposed to the sun. Usually it goes away on its own but I had such a bad reaction once after a trip to the Caribbean that I had to use antibiotics and steroid cream when I returned home. It actually scarred the skin on my arm and looked very much like the photo of your legs but it did fade over time. I don’t know if you have experienced a similar reaction to sun exposure but it sounds like you don’t spend much time in the sun. Believe it or not, I really spent almost all of the time in the shade most of my trip, primarily due to this condition, and I still had the absolute worst eruption. I don’t know if this could be a possible cause of your skin discolouration but you should definitely have a doctor look at it.

You need a referral to a dermatologist.

Dermatologist, STAT. Make note of any changes, great or small.

Definitely see a dermatologist, and take note of any changes in shade, color, texture, and thickness of dryness of skin. Do you have pain in this area?