Hello. Thanks for writing to us at healthcaremagic Judging from the description you gave I would keep a possibility of lip Vitiligo (mucosal). Vitiligo can affect the skin as well as mucosa. The patches on skin are usually milky white in color, whereas those on lip/mucosa are light pink in color because the underlying vasculature. Treatment of vitiligo depends on the extent of involvement and whether it is stable to spreading. Limited stable disease is treated with topical treatments whereas extensive Or spreading disease requires systemic treatment in addition to topical treatment. Since you have a single patch, you would like require just topical treatment. Commonly used topical treatment options are topical steroids, topical immunomodulators etc. I would suggest that you visit a dermatologist for a confirmatory diagnosis as well as appropriate treatment. Regards