Asked by: Alister Kennedy, Ayrshire
Almost all newborn children have some sort of birthmark. They are not hereditary but in some cases can be related to specific conditions caused by a gene mutation (though not a mutation passed on from a parent). In general, they appear because of abnormal blood vessels, or the nerves controlling the widening or narrowing of the blood vessels; or else because of clusters of overgrown pigmented cells.
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