Hello,
These spots on the knuckles can be due to contact dermatitis, dermatomyositis or lichen planus. Lichen planus is an inflammatory disease that causes a rash of purplish-red flat-topped bumps that are often very itchy. You should get these rashes evaluated from a dermatologist to confirm the diagnosis.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
I uploaded a photo of the knuckles of my left hand; where the spots have been the longest.
Sorry I don't know how to add the photo to my original question.
Please check my photos to reference the picture.
Thank you,
Andrea