Abstract

The epicanthic fold is the skin fold of the upper eyelid, covering the inner corner (medial canthus) of the eye. One of the primary facial features that are often closely associated with the epicanthic fold is elevation of the nasal bridge. There are various factors that influence whether epicanthic folds are formed, including ancestry, age, and certain medical conditions.

Factors | Geographic distribution

Epicanthic folds appear in East Asians, Southeast Asians, Central Asians, North Asians, some South Asians, Polynesians, Micronesians, Indigenous Americans (as well as Mestizos), the Khoisan, Malagasy, occasionally Europeans (e.g., Scandinavians, Hungarians, Samis, Irish and Poles) and among Nilotes.

Anthropologist Carleton S. Coon states that the "median fold" occurs in Finnic and Slavic populations, while the "true inner or mongoloid fold" appears in populations of the east and the far north.

Factors | Age

Many fetuses lose their epicanthic folds after three to six months of gestation.

Factors | Medical conditions

Epicanthic fold is sometimes found as a congenital abnormality. Medical conditions that cause the nasal bridge not to mature and project are associated with epicanthic folds. About 60% of individuals with Down syndrome (also called as trisomy 21) have prominent epicanthic folds. In 1862, John Langdon Down classified what is now called Down syndrome. He used the term "mongoloid" for the condition. This was derived from then-prevailing ethnic theory and from his perception that children with Down syndrome shared physical facial similarities (epicanthic folds) with those of Blumenbach's Mongolian race. While the term "mongoloid" (also "mongol" or "mongoloid idiot") continued to be used until the early 1970s, it is now considered pejorative and inaccurate and is no longer in common use about medical conditions.

In Zellweger syndrome, epicanthic folds are prominent.

Other examples are fetal alcohol syndrome, phenylketonuria, and Turner syndrome.