Birthmark
skin irregularity appearing around birth
A birthmark is a congenital, benign irregularity on the skin which is present at birth or appears shortly after birth—usually in the first month. Birthmarks can occur anywhere on the skin. They are caused by overgrowth of blood vessels, melanocytes, smooth muscle, fat, fibroblasts, or keratinocytes.
Dermatologists divide birthmarks into two types: pigmented birthmarks and vascular birthmarks. Pigmented birthmarks caused by excess skin pigment cells include: moles, café au lait spots, and Mongolian spots. Vascular birthmarks, also called red birthmarks, are caused by increased blood vessels and include macular stains (salmon patches), hemangiomas, and port-wine stains. A little over 1 in 10 babies have a vascular birthmark present by age 1. Several birthmark types are part of the group of skin lesions known as nevi or naevi, which is Latin for "birthmarks".
Birthmarks occur as a result of a localized imbalance in factors controlling the development and migration of skin cells. In addition, it is known that most vascular birthmarks are not hereditary.
This brief starts where responsible research should: with the source description of “Birthmark” as skin irregularity appearing around birth. Everything that follows is an evidence route, not borrowed authority.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Aug 29, 2026. The linked authority identifier is Q3513591. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Birthmark” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.