Hypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits (eyes), or orbital hypertelorism. In this condition the distance between the inner eye corners as well as the distance between the pupils is greater than normal. Hypertelorism should not be confused with telecanthus, in which the distance between the inner eye corners is increased but that of the outer eye corners remains unchanged. Therefore the distance between the pupils is normal.
Hypertelorism is a symptom in a variety of syndromes, including Edwards Syndrome (trisomy 18), 1q21.1 duplication syndrome, basal cell nevus syndrome, DiGeorge syndrome and Loeys-Dietz syndrome. Hypertelorism can also be seen in Apert syndrome, craniofrontonasal dysplasia, Noonan syndrome, neurofibromatosis, LEOPARD syndrome, Crouzon syndrome, Wolf-Hirschhorn syndrome, Andersen–Tawil syndrome, Waardenburg syndrome and cri du chat syndrome, along with piebaldism, prominent inner third of the eyebrows, irises of different color, spondyloepiphyseal dysplasia, mucopolysaccharide metabolism disorders (Morquio syndrome, Hurler’s syndrome), deafness and also in hypothyroidism. Some links have been found between Hypertelorism and Attention Deficit/Hyperactivity Disorder.