Could you attach a picture?
Yes, let me review them.
The appearance on the pictures is consistent with hemosiderin staining of the skin. When there has been trauma to the skin, there can be some leaking of blood into the tissue, which we see as a bruise. In some cases, the heme iron will deposit in a deep layer of skin and remain there indefinitely, similar to the way tattoo ink will remain in the skin.
This is not a concern and you do not need to be concerned about it.
It can commonly last months or years, and in some people, it may never go away.
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