Hello, yesterday I noticed a discoloration on my body, specifically my elbow . I noticed it while getting ready for a shower. There is no pain, the skin is a little dry, and it is noticeably darker than my right elbow. Also a Dark spot appeared on my lower abdomen on the lower left side about 3 weeks ago, right around the last rib, I felt no pain, and do not recall any bruising to cause either of these discoloration, there is no itching, or burning or anything. What may cause these effects on the body?